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1

Low thrust transfer optimisation of satellites formations to heliocentric Earth trailing orbits through a gradient restoration algorithm  

Microsoft Academic Search

When dealing with mission requirements calling for highly stable gravitational and thermal environments, one of the common options always considered is that of the heliocentric Earth trailing orbits (HETO). This is the case, for instance, of the Laser Interferometer Space Antenna (LISA), a joint ESA-NASA effort aimed at detecting gravitational radiation from deep-space sources, hence testing the fundamental gravitational theories.This

J. C Bastante; A Caramagno; L. F Peñ??n; M Belló-Mora; J Rodr??guez-Canabal

2004-01-01

2

Optimum rendezvous transfer between coplanar heliocentric elliptic orbits using solar sail  

Microsoft Academic Search

A convenient formulation is presented for determining the effect of terminal orbit eccentricities on the steering profile of a sail spacecraft for time-optimal rendezvous transfer between coplanar heliocentric orbits. The problem is reduced to that of solving a two-point boundary value problem for a system of seven ordinary differential equations. The system is solved using the controlled random search optimization

P. V. S. Rao; R. V. Ramanan

1992-01-01

3

Lifetimes of small bodies in planetocentric (or heliocentric) orbits  

Microsoft Academic Search

Stray bodies orbiting a planet or the Sun are removed by collisions with larger objects or by expulsion from the system. However, their rate of removal generally cannot be described by the simple exponential law used to describe radioactive decay, because their effective half-life lengthens with time. Previous studies of planetesimals, comets, asteroids, meteorites, and impact ejecta from planets or

Anthony R. Dobrovolskis; José L. Alvarellos; Jack J. Lissauer

2007-01-01

4

TEMPORARY CAPTURE OF PLANETESIMALS BY A PLANET FROM THEIR HELIOCENTRIC ORBITS  

SciTech Connect

When planetesimals encounter a planet, they can be temporarily captured by the planet's gravity and orbit about it for an extended period of time before escaping from the planet's vicinity. Such a process may have played an important role in the origin of irregular satellites or the dynamical evolution of short-period comets. Using three-body orbital integration, we study the temporary capture of planetesimals by a planet from their heliocentric eccentric orbits. We examine the dependence of the orbital characteristics during temporary capture as well as the rate of capture on the pre-capture heliocentric orbital parameters. We find that typical orbital size and direction of revolution around the planet change depending on planetesimals' initial eccentricity and energy. When initial eccentricity is so small that Kepler shear dominates the relative velocity between planetesimals and the planet, temporary capture typically occurs in the retrograde direction in the vicinity of the planet's Hill sphere, while large retrograde capture orbits outside the Hill sphere are predominant for large eccentricities. Long prograde capture occurs in a very narrow range of planetesimal eccentricity and energy. We obtain the rate of temporary capture of planetesimals and find that the rate of long capture increases with increasing eccentricity at low and high eccentricities, but decreases with increasing eccentricity in intermediate values of eccentricity. We also examine the dependence of capture rate on the duration of capture and find an approximate power-law dependence.

Suetsugu, Ryo; Ohtsuki, Keiji [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan); Tanigawa, Takayuki, E-mail: ryo3088@stu.kobe-u.ac.jp [Center for Planetary Science, Kobe University, Kobe 650-0047 (Japan)

2011-12-15

5

Poisson's theorem in heliocentric variables - Conditions for the application of this theorem concerning the invariability of the major axes of planetary orbits to second order in the masses  

Microsoft Academic Search

Poisson's theorem states that there is no secular inequality in the major axis of the orbits of the planets to the first and second approximation with respect to the masses. An analytical expression for the secular term of the major axes in heliocentric coordinates in the second approximation is derived, and it is shown that in heliocentric elements this term

L. Duriez

1978-01-01

6

heliocentric observations  

E-print Network

­ Garching) In order to cast more light on the problem of the cometary activity at large heliocentric perihelion, and also surveyed several more objects at various heliocentric distances. The enclosed table lists preliminary estimates of the nuclear radii for 4 comets, as well as the heliocentric distance

Meech, Karen Jean

7

Regarding the Accretion of 2003 VB12 (Sedna) and Like Bodies in Distant Heliocentric Orbits  

E-print Network

Recently, Brown et al. (2004) reported the exciting discovery of an ~800 km radius object, (90377) Sedna, on a distant, eccentric orbit centered at ~490 AU from the Sun. Here we undertake a first look exploring the feasibility of accreting this object and its possible cohorts between 75 AU (Sedna's perihelion distance) and 500 AU (Sedna's semi-major axis distance) from the Sun. We find such accretion possible in a small fraction of the age of the solar system, if such objects were initially on nearly circular orbits in this region, and if the solar nebula extended outward to distances far beyond the Kuiper Belt. If Sedna did form in situ, it is likely to be accompanied by a cohort of other large bodies in this region of the solar system.

S. A. Stern

2004-10-12

8

Regarding the Accretion of 2003 VB12 (Sedna) and Like Bodies in Distant Heliocentric Orbits  

Microsoft Academic Search

Recently, Brown et al. (2004) reported the exciting discovery of an ~800 km\\u000aradius object, (90377) Sedna, on a distant, eccentric orbit centered at ~490 AU\\u000afrom the Sun. Here we undertake a first look exploring the feasibility of\\u000aaccreting this object and its possible cohorts between 75 AU (Sedna's\\u000aperihelion distance) and 500 AU (Sedna's semi-major axis distance) from

S. Alan Stern

2004-01-01

9

Probes to the inferior planets—A new dawn for NEO and IEO detection technology demonstration from heliocentric orbits interior to the earth's?  

NASA Astrophysics Data System (ADS)

Recent years have seen a renewed interest in exploration of the interior of the solar system. A number of missions are currently under way, in planning as well as in space, with the primary goal to expand our knowledge on the planets Mercury and Venus. Chemical propulsion missions to Mercury in particular require an extended cruise phase prior to arrival at their destination, usually involving multiple planetary fly-by manoeuvres and many revolutions in heliocentric orbit. The difficulties in discovering and tracking small objects interior to Earth's orbit, mainly due to unfavourable viewing geometry as well as atmospheric interference, have long been noted by the solar system science and planetary defence communities. Space probes in the interior of the solar system are in a position to observe objects near or interior to Earth's orbit in favourable opposition geometry. They are also usually free from planet-related interference, at least while in cruise, and often can be while in planetary eclipse. Dedicated search and survey missions to look for Near and Inner Earth Objects (NEO, IEO) from the vicinity of Earth or low Earth orbit are being planned. In this article, the ad-hoc available as well as near-term planned in-situ capabilities of the optical instrument payloads of space probes to Venus and Mercury are compiled from publications by the respective instrument teams. The small-object detection capabilities of cameras and spectrographs in opposition geometry are estimated by a common method, using data from comparable instruments to supplement missing information where necessary. The on-board cameras are classified according to their small-object detection potential in a technology demonstration of asteroid detection from a heliocentric orbit substantially interior to Earth's.

Grundmann, Jan Thimo; Mottola, Stefano; Drentschew, Maximilian; Drobczyk, Martin; Kahle, Ralph; Maiwald, Volker; Quantius, Dominik; Zabel, Paul; van Zoest, Tim

2013-09-01

10

Probes to the Inferior Planets - A New Dawn for NEO and IEO Detection Technology Demonstration from Heliocentric Orbits Interior to the Earth's?  

NASA Astrophysics Data System (ADS)

With the launch of MESSENGER and VENUS EXPRESS, a new wave of exploration of the inner solar system has begun. Noting the growing number of probes to the inner solar system, it is proposed to connect the expertise of the respective spacecraft teams and the NEO and IEO survey community to best utilize the extended cruise phases and to provide additional data return in support of pure science as well as planetary defence. Several missions to Venus and Mercury are planned to follow in this decade. Increased interest in the inferior planets is accompanied by several missions designed to study the Sun and the interplanetary medium (IPM) from a position near or in Earth orbit, such as the STEREO probes and SDO. These augment established solar observation capabilities at the Sun-Earth L1 Lagrangian point such as the SOHO spacecraft. Thus, three distinct classes of spacecraft operate or observe interior to Earth's orbit. All these spacecraft carry powerful multispectral cameras optimized for their respective primary targets. MESSENGER is scheduled to end its six-year interplanetary cruise in March 2011 to enter Mercury orbit, but a similarly extended cruise with several gravity-assists awaits the European Mercury mission BEPICOLOMBO. Unfortunately, the automatic abort of the orbit insertion manoeuvre has also left AKATSUKI (a.k.a. Venus Climate Orbiter (VCO), Planet-C) stranded in heliocentric orbit. After an unintended fly-by, the probe will catch up with Venus in approximately six years. Meanwhile, it stays mostly interior to Venus in a planet-leading orbit. In addition to the study of comets and their interaction with the IPM, observations of small bodies akin to those carried out by outer solar system probes are occasionally attempted with the equipment available. The study of structures in the interplanetary dust (IPD) cloud has been a science objective during the cruise phase of the Japanese Venus probe AKATSUKI from Earth to Venus. IPD observations in the astronomical H-band (1.65 ?m) are supported by its IR2 camera down to 1.5 ?W/m2sr in single 2 minute exposures. In the same setting, point sources of 13 mag can be detected. Obviously, a number of large asteroids exceed this threshold. The EARTHGUARD-I study, completed in 2003 by the DLR Institute of Planetary Research and Kayser-Threde under ESA contract, proposed a dedicated steerable 020...35 cm telescope and CCD camera payload on a probe to the inner solar system, to detect Near-Earth and Inner-Earth Objects (NEOs, IEOs) in favourable opposition geometry. A ride- share on a Mercury orbiter and a dedicated low-thrust propulsion spacecraft to a heliocentric 0.5 AU orbit were studied. A similar-sized telescope is presently being developed for the ASTEROIDFINDER satellite of DLR. Therefore, the technical feasibility of a number of asteroid observation scenarios involving spacecraft and targets interior to Earth's orbit is assessed based on the latest available spacecraft information and asteroid population models. A rough estimate of the required effort in terms of ground-based spacecraft operations and on-board resources is given for selected representative scenarios.

Grundmann, J. T.; Mottola, S.; Drentschew, M.; Drobczyk, M.; Kahle, R.; Maiwald, V.; Quantius, D.; Zabel, P.; Van Zoest, T.

2011-11-01

11

Kepler's winding Path to true Heliocentrism  

NASA Astrophysics Data System (ADS)

The paper concerns the evolution of concepts by Johannes Kepler from Aristotelian conception of the Universe to Heliocentrism. Already as young Magister in Tubingen Kepler has taken an active part in Physical disputations of the candidates and has defended the doctrines of Copernik (1). In the Mysterium Cosmographicum he refers the planetary distances no longer to the center of the earth's orbit, but to the center of the true sun. But just by working out his Astronomia Nova Kepler succeeds in creating a strictly heliocentric astronomy as his handwriting Manuscripts give detailed information (2). Notes: 1) fragmentum orations de motu terrae. In Keppler Gesammelte werke Vol. 20.1, Munich 1988, p. 147-149 2) Commentaria in Theoriam Martis. Edition in: Kepler Gessamelete Werke Vol. 20.2 (in preparation)

Bialas, Volker

12

Simulations of the Solar Orbiter spacecraft interactions with the Solar wind at different heliocentric distances: effects on SWA-EAS measurements  

NASA Astrophysics Data System (ADS)

This presentation focuses on numerical simulations of the Solar Orbiter spacecraft/plasma interactions performed with the Spacecraft Plasma Interaction System (SPIS) software (http://dev.spis.org/projects/spine/home/spis/). This toolkit aims at modelling spacecraft-plasma interactions, based on an electrostatic 3-D unstructured particle-in-cell plasma model. New powerful SPIS functionalities were recently delivered within the extension of the software: SPIS-Science (ESA contract). This version revolutionizes spacecraft/plasma interactions as users are now able to model and configure plasma instrument such as Langmuir probes or particle detectors taking into account instrument characteristics like geometry, materials, energy ranges and resolution, output frequency, field of view ... In the validation context of SPIS-Science functionalities, a simulation campaign was carried out, including several cases of the ESA Solar Orbiter mission. The results presented here specifically focus on particle measurements through the modelling of the Solar Wind Analyzer - Electron Analyzer System instrument (SWA-EAS). Simulations of the spacecraft in different environments have been performed and extensively analysed. A detailed analysis will be presented concerning 1/ the satellite charging and, in particular, differential potentials on the dielectric surfaces of the Solar panels and the High Gain Antenna, which may severely affect low energy EAS measurements, 2/ the surrounding plasma behaviour : potential barriers for secondary and photoelectrons of about -5 V around the vehicle are indeed observed at the mission perihelion of 0.28 AU from the Sun and 3/ a quantification of biases on EAS measurements due to the combined effects of surface potentials, ion wake, and potential barriers. This work proposes a general framework to prepare the analysis of the future Solar Orbiter measurements.

Guillemant, S.; Genot, V. N.; Matéo Vélez, J.; Sarrailh, P.; Louarn, P.; Maksimovic, M.; Owen, C. J.; Hilgers, A. M.

2013-12-01

13

A Space weather information service based upon remote and in-situ measurements of coronal mass ejections heading for Earth. A concept mission consisting of six spacecraft in a heliocentric orbit at 0.72 AU  

NASA Astrophysics Data System (ADS)

The Earth's magnetosphere is formed as a consequence of interaction between the planet's magnetic field and the solar wind, a continuous plasma stream from the Sun. A number of different solar wind phenomena have been studied over the past 40 years with the intention of understanding and forecasting solar behavior. One of these phenomena in particular, Earth-bound interplanetary coronal mass ejections (CMEs), can significantly disturb the Earth's magnetosphere for a short time and cause geomagnetic storms. This publication presents a mission concept consisting of six spacecraft that are equally spaced in a heliocentric orbit at 0.72 AU. These spacecraft will monitor the plasma properties, the magnetic field's orientation and magnitude, and the 3D-propagation trajectory of CMEs heading for Earth. The primary objective of this mission is to increase space weather forecasting time by means of a near real-time information service, that is based upon in-situ and remote measurements of the aforementioned CME properties. The obtained data can additionally be used for updating scientific models. This update is the mission's secondary objective. In-situ measurements are performed using a Solar Wind Analyzer instrumentation package and fluxgate magnetometers, while for remote measurements coronagraphs are employed. The proposed instruments originate from other space missions with the intention to reduce mission costs and to streamline the mission design process. Communication with the six identical spacecraft is realized via a deep space network consisting of six ground stations. They provide an information service that is in uninterrupted contact with the spacecraft, allowing for continuous space weather monitoring. A dedicated data processing center will handle all the data, and then forward the processed data to the SSA Space Weather Coordination Center which will, in turn, inform the general public through a space weather forecast. The data processing center will additionally archive the data for the scientific community. The proposed concept mission allows for major advances in space weather forecasting time and the scientific modeling of space weather.

Ritter, Birgit; Meskers, Arjan J. H.; Miles, Oscar; Rußwurm, Michael; Scully, Stephen; Roldán, Andrés; Hartkorn, Oliver; Jüstel, Peter; Réville, Victor; Lupu, Sorina; Ruffenach, Alexis

2015-02-01

14

The cometary outbursts at large heliocentric distances  

Microsoft Academic Search

A model is presented explaining changes in cometary brightness during an outburst at large heliocentric distances. It is shown that a combination of the following effects can explain the main characteristics of outburst at large heliocentric distances: the specific exothermic processes in cometary nucleus (as the HCN polymerisation and the crystallization of the water amorphous ice, connected with the ejection

P. Gronkowski; J. Smela

1998-01-01

15

Planetocentric versus heliocentric impacts in the Jovian and Saturnian satellite system  

Microsoft Academic Search

Readily applicable equations are derived for calculating the impact velocities, collision intervals, and cumulative crater frequencies in a satellite system for planetocentric and heliocentric impactors. Observed cumulative crater frequencies in the Saturnian satellite system and a sometimes observed lack of apex-antapex asymmetry of crater frequencies favor crater-producing projectiles orbiting initially in elliptic orbits round the parent planet (planetocentric impactors). On

G. P. Horedt; G. Neukum

1984-01-01

16

Fundamentals Solution of the orbit  

E-print Network

heliocentric models DYNAMICS OF GALAXIES Two-body problem Piet van der Kruit Kapteyn Astronomical Institute heliocentric models Contents Fundamentals The fundamental equations Center of gravity Angular momentum Solution's third law Kepler's equation Orbital parametrs Geocentric versus heliocentric models The geocentric model

Kruit, Piet van der

17

Symplectic Correctors for Canonical Heliocentric N-Body Maps Massachusetts Institute of Technology, Cambridge, MA 02139  

E-print Network

--gravitation--methods: analytical, numerical #12;­ 3 ­ 1. Introduction Symplectic correctors, introduced by Wisdom et al. (1996 heliocentric coordinates (Wisdom 1992; Touma and Wisdom 1994). Indeed, the planetary orbit part of our effects could be removed by canonical perturbation theory. A similar trick was used earlier in our papers

Wisdom, Jack

18

Optimal three-dimensional heliocentric solar-sail rendezvous transfer trajectories  

Microsoft Academic Search

This study is concerned with the problem of optimization of the control, in the sense of high speed of response, for minimum time rendezvous transfer of sail-spacecraft between heliocentric, inclined, elliptic orbits. The angles defining the orientation of the sail (assumed to be perfectly reflecting and flat) with respect to sunlight are the control variables. The analysis employs a two-body

P. V. Subba Rao; R. V. Ramanan

1993-01-01

19

Ancient Greek Heliocentric Views Hidden from Prevailing Beliefs?  

NASA Astrophysics Data System (ADS)

We put forward the working hypothesis that the heliocentric, rather than the geocentric view, of the Solar System was the essential belief of the early Greek philosophers and astronomers. Although most of them referred to the geocentric view, it is plausible that the prevalent religious beliefs about the sacred character of the Earth as well as the fear of prosecution for impiety (asebeia) prevented them from expressing the heliocentric view, even though they were fully aware of it. Moreover, putting the geocentric view forward, instead, would have facilitated the reception of the surrounding world and the understanding of everyday celestial phenomena, much like the modern presentation of the celestial sphere and the zodiac, where the Earth is at the centre and the Sun makes an apparent orbit on the ecliptic. Such an ingenious stance would have set these early astronomers in harmony with the dominant religious beliefs and, at the same time, would have helped them to 'save the appearances', without sacrificing the essence of their ideas. In Hellenistic and Roman times, the prevailing view was still the geocentric one. The brilliant heliocentric theory advanced by Aristarchos in the early third century B.C. was never established, because it met with hostility in Athens - Aristarchos was accused of impiety and faced the death penalty. The textual evidence suggests that the tight connection which existed between religion and the city-state (polis) in ancient Greece, and which led to a series of impiety trials against philosophers in Athens during the fifth and fourth centuries B.C., would have made any contrary opinion expressed by the astronomers seem almost a high treason against the state.

Liritzis, Ioannis; Coucouzeli, Alexandra

2008-03-01

20

Planar heliocentric roto-translatory motion of a spacecraft with a solar sail of complex shape  

Microsoft Academic Search

A complete treatment of the general motion of rotation and translation of a solar-sail spacecraft is proposed for the non-flat sail of complex shape. The planar heliocentric roto-translatory motion is considered, orbit-rotational coupling in the problem of altitude and orbital sail motion is investigated for the two-folding sail formed by two unequal reflective rectangular plates oriented at a right angle.

S. N. Kirpichnikov; E. S. Kirpichnikova; E. N. Polyakhova; A. S. Shmyrov

1995-01-01

21

Analytical control laws of the heliocentric motion of the solar sail spacecraft  

NASA Astrophysics Data System (ADS)

The heliocentric motion of the solar sail spacecraft is described in classical Keplerian elements. The flat of solar sail with an ideal reflection coefficient is considered. The spacecraft performs a noncoplanar motion with the sun gravity and the light pressure. Disturbances of other celestial bodies gravity are not considered. We have received analytical terms for laws to control a solar sail, which ensure constancy or maximum rate of change of the Keplerian elements. To confirm the results correctness, we simulated the solar sail spacecraft. The spacecraft's initial orbit coincides with the average Earth orbit relative to the Sun. Authors developed a program complex to simulated the planar heliocentric movement and obtained results for motion simulation of flights to Mars and Venus. The results were compared with the simulation results obtained using the Pontryagin maximum principle.

Gorbunova, Irina; Starinova, Olga

2014-12-01

22

Comet Hale-Bopp at large heliocentric distance  

NASA Astrophysics Data System (ADS)

The objective is to determine the size, shape, and possible presence of a small, possibly bound, companion. The latter has been reported by Marchis et al. using the ADONIS adaptive optics system on the ESO 3.6 meter telescope. They claim separations of the two components of 0.23'' {November 1997} and 0.36'' {January 1998} when the comet was 3.3 and 4.1 AU from the Sun. Such a companion is not evident in any STIS images recorded by Weaver et al., but these were single snapshots in time and the companion may have been occulted. The discovery of a bound companion, and the subsequent determination of its orbital period, would provide the first determination of a cometary mass and the density of a cometary nucleus. At large heliocentric distances there will still be residual dust coma so the highest possible spatial resolution {HRC near 300 nm} is needed to model the coma and photometrically isolate the nucleus. The near infrared is best suited for evaluation of the spatial distribution of the dust coma. With proper choice of filter it is also possible to search for a gas coma {CN at 388 nm}. Ideally the comet should be imaged over a complete 11.3 hour rotation period, but a half period would be sufficient to obtain an idea of the shape of the reflecting body. Hale-Bopp is visible throughout 2002. During the period 1 March 2002 to 28 February 2003 the heliocentric distance increases from 15.2 to 17.3 AU. The expected nucleus magnitude {visible} is 16.5-17.0

Ford, Holland

2002-07-01

23

The Heliocentric Variation of the Properties of Interplanetary Field Enhancement  

NASA Astrophysics Data System (ADS)

Interplanetary Field Enhancements (IFEs) are increases of the interplanetary magnetic field usually to a sharp maximum and containing a current sheet near the center of the event. They have been observed at Helios and MESSENGER as close as 0.3 AU to the Sun, at VEX and PVO at 0.72 AU; at STEREO, ACE, Wind, Geotail, ARTEMIS at 1 AU and Ulysses from 1 to 5 AU. Our model for the physical mechanism for creating these disturbances is that collisions of bodies in the size range 10 - 1000m are catastrophically disrupted by a collision with a fast moving smaller object. The rate of detection of IFEs is dependent on heliocentric range increasing closer to the Sun. There are several possible reasons for this increase which we explore. The mass of the dust cloud that is picked up is significant about 108kg. The magnetic gradient force of the IFE is large enough to lift this mass through the Sun's gravitational potential wall. The momentum transfer that enables this outward transport is a small fraction of the solar wind momentum flux but this transfer can be detected using superposed epoch studies of the solar wind, and is consistent with the hypothesis. We note that the rate of IFE observations in the Helios and MESSENGER data at 0.3 AU is less than expected from extrapolating the observations at and beyond 0.7 AU. This result can soon be extended closer to the Sun with Solar Orbiter and Solar Probe Plus.

Lai, H.; Russell, C. T.; Wei, H.; Zhang, T.

2013-05-01

24

HELIOCENTRIC EVOLUTION OF THE DEGRADATION OF POLYOXYMETHYLENE. APPLICATION TO THE ORIGIN OF  

E-print Network

HELIOCENTRIC EVOLUTION OF THE DEGRADATION OF POLYOXYMETHYLENE. APPLICATION TO THE ORIGIN wavelength observations (Biver et al., 2002a) showed a steep increase with decreasing heliocentric distance. We studied the heliocentric evolution of the degradation of polyoxymethylene (formaldehyde polymers

Demoulin, Pascal

25

M-Dwarfs at Large Heliocentric Distances  

E-print Network

We present an analysis of the faint M star population seen as foreground contaminants in deep extragalactic surveys. We use space-based data to separate such stars from high redshift galaxies in a publically-available dataset, and consider the photometric properties of the resulting sample in the optical and infrared. The inferred distances place these stars well beyond the scale height of the thick disk. We find strong similarities between this faint sample (reaching i'_{AB}=25) and the brighter disk M dwarf population studied by other authors. The optical-infrared properties of the bulk of our sources spanning 6000A-4.5microns are consistent with those 5-10 magnitudes brighter. We also present deep spectroscopy of faint M dwarf stars reaching continuum limits of i'_{AB}~26, and measure absorption line strengths in the CaH2 and TiO5 bands. Both photometrically and spectroscopically, our sources are consistent with metallicities as low as a tenth solar: metal-rich compared with halo stars at similar heliocentric distances. We comment on the possible MACHO identification of M stars at faint magnitudes.

E. R. Stanway; M. N. Bremer; M. D. Lehnert; J. J. Eldridge

2007-11-15

26

Heliocentric zoning of the asteroid belt by aluminum-26 heating  

NASA Technical Reports Server (NTRS)

Variations in petrology among meteorites attest to a strong heating event early in solar system history, but the heat source has remained unresolved. Aluminum-26 has been considered the most likely high-energy, short-lived radionuclide (half-life 0.72 million years) since the discovery of its decay product - excess Mg-26 - in Allende CAI's. Furthermore, observation of relict Mg-26 in an achondritic clast and in feldspars within ordinary chondrites (3,4) provided strong evidence for live Al-26 in meteorite parent bodies and not just in refractory nebular condensates. The inferred amount of Al-26 is consistent with constraints on the thermal evolution of both ordinary and carbonaceous chondrite parent objects up to a few hundred kilometers in diameter. Meteorites can constrain the early thermal evolution of their parent body locations, provided that a link can be established between asteroid spectrophotometric signature and meteorite class. Asteroid compositions are heliocentrically distributed: objects thought to have experienced high metamorphic or even melting temperatures are located closer to the sun, whereas apparently unaltered or mildly heated asteroids are located farther away. Heliocentric zoning could be the result of Al-26 heating if the initial amount of the radionuclide incorporated into planetesimals was controlled by accretion time, which in turn varies with semimajor axis. Analytic expressions for planetary accretion may be integrated to given the time, tau, required for a planetesimal to grow to a specified radius: tau varies as a(sup n), where n = 1.5 to 3 depending on the assumptions about variations in the surface density of the planetesimal swarm. Numerical simulations of planetesimal accretion at fixed semimajor axis demonstrate that variations in accretion time among small planetesimals can be strongly nonlinear depending on the initial conditions and model assumptions. The general relationship with semimajor axis remains valid because it depends only on the initial orbit properties and distribution of the planesimal swarm. In order to demonstrate the basic dependence of thermal evolution on semimajor axis, we parameterized accretion time across the asteroid belt according to tau varies as a(sup n) and calculated the subsequent thermal history. Objects at a specified semimajor axis were assumed to have the same accretion time, regardless of size. We set the initial Al-26/Al-27 ratio = 6 x 10(exp -5) and treated n and tau(sub 0) at a(sub 0) = 3 AU as adjustable parameters. The thermal model included temperature-dependent properties of ice and rock (CM chondrite analog) and the thermodynamic effects of phase transitions.

Grimm, R. E.; Mcsween, H. Y., Jr.

1993-01-01

27

Proof-of-Concept Trajectory Designs for a Multi-Spacecraft, Low-Thrust Heliocentric Solar Weather Buoy Mission  

NASA Technical Reports Server (NTRS)

A new solar weather mission has been proposed, involving a dozen or more small spacecraft spaced at regular, constant intervals in a mutual heliocentric circular orbit between the orbits of Earth and Venus. These solar weather buoys (SWBs) would carry instrumentation to detect and measure the material in solar flares, solar energetic particle events, and coronal mass ejections as they flowed past the buoys, serving both as science probes and as a radiation early warning system for the Earth and interplanetary travelers to Mars. The baseline concept involves placing a mothercraft carrying the SWBs into a staging orbit at the Sun-Earth L1 libration point. The mothercraft departs the L1 orbit at the proper time to execute a trailing-edge lunar flyby near New Moon, injecting it into a heliocentric orbit with its perihelion interior to Earth s orbit. An alternative approach would involve the use of a Double Lunar Swingby (DLS) orbit, rather than the L1 orbit, for staging prior to this flyby. After injection into heliocentric orbit, the mothercraft releases the SWBs-all equipped with low-thrust pulsed plasma thrusters (PPTs)-whereupon each SWB executes a multi-day low-thrust finite bum around perihelion, lowering aphelion such that each achieves an elliptical phasing orbit of different orbital period from its companions. The resulting differences in angular rates of motion cause the spacecraft to separate. While the lead SWB achieves the mission orbit following an insertion burn at its second perihelion passage, the remaining SWBs must complete several revolutions in their respective phasing orbits to establish them in the mission orbit with the desired longitudinal spacing. The complete configuration for a 14 SWB scenario using a single mothercraft is achieved in about 8 years, and the spacing remains stable for at least a further 6 years. Flight operations can be simplified, and mission risk reduced, by employing two mothercraft instead of one. In this scenario: the second mothercraft stays in a libration-point or DLS staging orbit until the first mothercraft has achieved nearly 180 separation from the Earth. The timing of the second mothercraft's subsequent lunar flyby is planned such that this spacecraft will be located 180 from the first mothercraft upon completion of its heliocentric circularization maneuvers. Both groups of satellites then only have to spread out over 180 to obtain full 360 coverage around the Sun.

Muller, Ronald; Franz, Heather; Roberts, Craig; Folta, Dave

2005-01-01

28

Orbits  

NSDL National Science Digital Library

This Topic in Depth explores the Web's offerings on Orbits. The first site is offered by Northwestern University and asks: What is an orbit? (1 ). The site answers questions such as What causes an orbit to happen?, What is a satellite?, What travels in an orbit?, and Are there orbits within orbits?. A great starting site for this subject, visitors should come away with a broad and clear description of the topic. The second site, called Orbit Diagrams (2 ) is provided by the Harvard-Smithsonian Center for Astrophysics. The diagrams are "intended to aid in the visualization of the three-dimensional nature of the orbits and how they are orientated with respect to the orbit of the earth." Next, from the University of Wisconsin-Madison Department of Astronomy comes the Moon Phases (3 ) interactive Web site. Users are able to animate the moon's orbit in various phases and views as well as learn all the names of the phases. The fourth site is another virtual visualization tool provided by NASA's Near Earth Object Program called Orbits (4 ). The site lets users enter the designation or name of any asteroid or comet and then view the three-dimensional orbit of that object. The next site, maintained by the Conservation, Astronomy, Physics and Soaring Page, is called Satellite Orbits - Gravitational Assist from Planets (5 ). The site contains information on Kepler's Laws, which apply to elliptical orbits involving two bodies, hyperbolic orbits, relative motion, and the gravitational sphere of influence. The sixth site is an educational lesson provided by Dr. Richard L. Bowman of Bridgewater College called Planetary Orbit Exercise (6 ). Students are given information on Keplar's Laws of Planetary Motion, a list of definitions, links to outside sites for additional information, and then several questions to answer. The Planetary Physical Data (7 ) page is part of the larger Smithsonian Center for Earth and Planetary Studies Web site. Visitors will find a list of planets along with various information such as their relative sidereal period of orbit, mean orbital velocity, orbital eccentricity, and much more. The last site related to orbits is an educational activity provided by the Physics Classroom called Circular Motion and Planetary Motion (8 ). Four lessons are presented including Motion Characteristics for Circular Motion, Applications of Circular Motion, Universal Gravitation, and Planetary and Satellite Motion. Each contain clear and well written descriptions along with all the necessary information for successful completion.

Brieske, Joel A.

29

3D high-speed escape heliocentric trajectories by all-metallic-sail low-mass sailcraft  

Microsoft Academic Search

Considering a photon solar-sail spacecraft with a lightness number in the range [12–1) (all-metallic sail), this paper analyses a class of heliocentric trajectories, characterized by orbital angular-momentum reversal, delivering a considerable cruise speed (10–20 AU\\/yr) and allowing a sailcraft to access any celestial latitude [??2, +?2], depending primarily on the perihelion distance. It is found out that, if the lightness

Giovanni Vulpetti

1996-01-01

30

A general planetary theory in elliptical heliocentric variables  

Microsoft Academic Search

The work proposes an analytical theory that generalizes Verrier's classical theory. The motion of planets about the sun is described in the neighborhood of uniform circular coplanar motions by elliptical osculating heliocentric elements. The variations of these elements are expressed in series with periodic terms: secular terms (with periods greater than 50,000 years), and short-period terms whose amplitudes are functions

L. Duriez

1979-01-01

31

Back to the Future: The Return to Heliocentrism  

E-print Network

to the Sun, p2 = a3 #12;Galileo Galilei (1564-1642) · The first experimental physicist? ­ Demonstrated stars in the Milky Way #12;#12;#12;#12;Galileo vs. the Pope · The Catholic Church was not anti, heliocentric cosmology · But Galileo insulted Pope Urban VIII in his book Dialogue Concerning the Two Chief

Walter, Frederick M.

32

Pioneer 10 studies of interplanetary shocks at large heliocentric distances  

Microsoft Academic Search

Pioneer 10 Ames plasma analyzer data collected in the 6.1 to 12.6 AU range of heliocentric distances (November 1974 to April 1977) have been examined for interplanetary shock waves. Eighteen shock signatures have been identified, with four of these being of the reverse type and the remainder the forward type. Sonic Mach numbers in the range from 3 to 10

J. D. Mihalov; J. H. Wolfe

1979-01-01

33

Heliocentric distance dependence of the interplanetary magnetic field  

Microsoft Academic Search

Recent and ongoing planetary missions have provided and are continuing to provide extensive observations of the variations of the interplanetary magnetic field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations are observed. These are produced predominantly by dynamical processes in the interplanetary medium associated with stream interactions.

Kenneth W. Behannon

1978-01-01

34

Heliocentric zoning of the asteroid belt by aluminum-26 heating  

Microsoft Academic Search

The dependence of asteroid spectral class (and inferred composition and thermal history) on heliocentric radius has been held to be the result of heating by a solar energy source, most likely electrical induction, during the formation of the planetary system. Such variations in thermal history can be more simply explained by the presence of different amounts of the radionuclide aluminum-26,

R. E. Grimm; H. Y. Jr. McSween

1993-01-01

35

Activity of comets at large heliocentric distances pre-perihelion  

Microsoft Academic Search

We present observational data for two long-period and three dynamically new comets observed at heliocentric distances between 5.8 to 14.0 AU. All of the comets exhibited activity beyond the distance at which water ice sublimation can be significant. We have conducted experiments on gas-laden amorphous ice samples and show that considerable gas emission occurs when the ice is heated below

K. J. Meech; J. Pittichová; A. Bar-Nun; G. Notesco; D. Laufer; O. R. Hainaut; S. C. Lowry; D. K. Yeomans; M. Pitts

2009-01-01

36

Shock-associated energetic proton events at large heliocentric distances  

Microsoft Academic Search

Enhancements of energetic protons (> or approx. =0.5 MeV) in association with forward-reverse shock pairs have been observed at large heliocentric distances. An interpretation of the time profiles of these events is offered in terms of a model of solar wind stream structure. Persistent sweeping of energetic particles by each shock front and their banking-up by reflection lead to the

I. D. Palmer; J. T. Gosling

1978-01-01

37

Dust emission from comets at large heliocentric distances  

Microsoft Academic Search

Possible mechanisms for the production of the extended dust coma observed in comet Bowell (1980b) at the large heliocentric distance of 7.17 AU are considered. It is concluded that a plausible mechanism is electrostatic blow-off of fine, loose dust from an electrically charged H2O dominated nucleus, as recently proposed by Mendiset al. (1981). Of all the other processes considered, dust

Harry L. F. Houpis; D. A. Mendis

1981-01-01

38

ICARUS 96,43-64 (1992) Orbital Stability Zones about Asteroids  

E-print Network

ICARUS 96,43-64 (1992) Orbital Stability Zones about Asteroids II.The Destabilizing Effects-131) characterized the size and shape of a stability zone around an asteroid on a circular heliocentric orbit within analytically and numerically: the asteroid's nonzero heliocentric eccentricity and solar radiation pressure

Hamilton, Douglas P.

39

Heteroclinic connections between periodic orbits and resonance transitions in celestial mechanics  

E-print Network

heliocentric orbit is typi- cally close to the 3:2 resonance three revolutions around the Sun in two Jupiter periods while the exterior heliocentric orbit is near the 2:3 resonance two revolutions around the Sun in three Jupiter periods . An important feature of the dynamics of these comets is that during

Ross, Shane

40

CCD-photometry of comets at large heliocentric distances  

NASA Technical Reports Server (NTRS)

CCD imaging and time series photometry are used to determine the state of activity, nuclear properties and eventually the rotational motion of cometary nuclei. Cometary activity at large heliocentric distances and mantle evolution are not yet fully understood. Results of observations carried out at the 2.1 telescope on Kitt Peak April 10-12 and May 15-16, 1991 are discussed. Color values and color-color diagrams are presented for several comets and asteroids. Estimations of nuclear radii and shapes are given.

Mueller, Beatrice E. A.

1992-01-01

41

Heliocentric distance dependence of the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Recent and ongoing planetary missions have provided extensive observations of the variations of the Interplanetary Magnetic Field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations were observed. These are produced predominantly by dynamical processes in the interplanetary medium associated with stream interactions. Magnetic field variations near the sun are propagated to greater heliocentric distances, also contributing to the observed variablity of the IMF. Temporal variations on a time-scale comparable to or less than the corotation period complicate attempts to deduce radial gradients of the field and its fluctuations from the various observations. However, recent measurements inward to 0.46 AU and outward to 5 AU suggest that the radial component of the field on average decreases approximately as r to the minus second power, while the azimuthal component decreases more rapidly than the r to the minum first power dependence predicted by simple theory. This, and other observations, are discussed.

Behannon, K. W.

1977-01-01

42

On the Provability of Heliocentrism. I. Ole Roemer and the Finite Speed of Light  

NASA Astrophysics Data System (ADS)

This paper describes observational support of heliocentrism during the late Renaissance. Initiated by Galileo's clues from telescopic sightings, the first indirect quantitative support for the heliocentric doctrine resulted from accurate eclipse timings of the , made possible by breakthroughs in technology (telescope optics and the pendulum clock) and driven by the quest for longitude at sea and on land. The resulting discovery of Olaus Roemer that the velocity of light is finite, is an indirect argument supporting heliocentrism.

Sterken, Christiaan

2007-10-01

43

Microlens Masses from 1-D Parallaxes and Heliocentric Proper Motions  

NASA Astrophysics Data System (ADS)

One-dimensional (1-D) microlens parallaxes can be combined with heliocentric lens-source relative proper motion measurements to derive the lens mass and distance, as suggested by Ghosh et al. (2004). Here I present the first mathematical anlysis of this procedure, which I show can be represented as a quadratic equation. Hence, it is formally subject to a two-fold degeneracy. I show that this degeneracy can be broken in many cases using the relatively crude 2-D parallax information that is often available for microlensing events. I also develop an explicit formula for the region of parameter space where it is more difficult to break this degeneracy. Although no mass/distance measurements have yet been made using this technique, it is likely to become quite common over the next decade.

Gould, Andrew

2014-12-01

44

Application of the heliocentric potential to aircraft dosimetry.  

PubMed

The heliocentric potential is the result of a steady-state solution to the diffusion equation of cosmic rays through the solar wind. The counting rate of any high-latitude, ground-level neutron monitor can be used to determine this potential, which will return cosmic ray spectra in real time. These spectra are routinely used to determine the radiation dose rate to which air crew are exposed during the precise hours of a flight, including the effects of quick decreases and Forbush decreases. Further, it has been used in an effort to calculate the radiation dose rate to air crew during an energetic solar particle event, as the cosmic ray background before the event must be determined. An alternate approach is to use the deceleration potential, which assumes a significant time-dependence of cosmic rays through the heliosphere. However, the theory behind it does not account for the behaviour of ground-level neutron monitors. PMID:16604656

O'Brien, Keran; Felsberger, Ernst; Kindl, Peter

2005-01-01

45

Microlens Masses from 1-D Parallaxes and Heliocentric Proper Motions  

E-print Network

One-dimensional (1-D) microlens parallaxes can be combined with heliocentric lens-source relative proper motion measurements to derive the lens mass and distance, as suggested by Ghosh et al. (2004). Here I present the first mathematical anlysis of this procedure, which I show can be represented as a quadratic equation. Hence, it is formally subject to a two-fold degeneracy. I show that this degeneracy can be broken in many cases using the relatively crude 2-D parallax information that is often available for microlensing events. I also develop an explicit formula for the region of parameter space where it is more difficult to break this degeneracy. Although no mass/distance measurements have yet been made using this technique, it is likely to become quite common over the next decade.

Gould, Andrew

2014-01-01

46

Heliocentric distance and temporal dependence of the interplanetary density-magnetic field magnitude correlation  

Microsoft Academic Search

The Helios, IMP 8, ISEE 3, and Voyager 2 spacecraft are used to examine the solar cycle and heliocentric distance dependence of the correlation between density n and magnetic field magnitude B in the solar wind. previous work had suggested that this correlation becomes progressively more negative with heliocentric distance out to 9.5 AU. Here they show that this evolution

D. A. Roberts

1990-01-01

47

32ND INTERNATIONAL COSMIC RAY CONFERENCE, BEIJING 2011 Heliocentric Distance of CMEs at the Time of Energetic Particle Release: Revisit-  

E-print Network

32ND INTERNATIONAL COSMIC RAY CONFERENCE, BEIJING 2011 Heliocentric Distance of CMEs at the Time, and the finite size of the pre-eruption CME structure, we derive the heliocentric release distance particles are released when the CMEs reach an average heliocentric distance of ~3.6 solar radii (Rs

Usoskin, Ilya G.

48

Pioneer 10 observation of the solar wind proton temperature heliocentric gradient  

NASA Technical Reports Server (NTRS)

Solar wind isotropic proton temperatures as measured out to 12.2 AU heliocentric distance by the Ames plasma analyzer aboard Pioneer 10 are presented as consecutive averages over three Carrington solar rotations and discussed. The weighted least-squares fit of average temperature to heliocentric radial distance, R, yields the power law R sup -.52. These average proton temperatures are not correlated as well with Pioneer 10's heliocentric radial distance (-.85) as are the corresponding average Zurich sunspot numbers R sub z (-.95). Consequently, it is difficult to isolate the spatial gradient in the Pioneer 10 solar wind proton temperatures using that data alone.

Mihalov, J. D.; Wolfe, J. H.

1978-01-01

49

Pioneer10 observation of the solar wind proton temperature heliocentric gradient  

Microsoft Academic Search

Solar wind isotropic proton temperatures as measured out to 12.2 AU heliocentric distance by the Ames plasma analyzer aboard Pioneer-10 are presented as consecutive averages over three Carrington solar rotations and discussed. The weighted least-squares fit of average temperature to heliocentric radial distance, R, yields the power law R-0.52. These average proton temperatures are not correlated as well with Pioneer-10's

J. D. Mihalov; J. H. Wolfe

1978-01-01

50

The trend of production rates with heliocentric distance for comet P\\/Halley  

Microsoft Academic Search

Comet P\\/Halley was observed spectroscopically in the wavelength range 5200-10,400 A during 10 observing runs, roughly a month apart from 1985 August 28 to 1986 June 6. The observations span a heliocentric distance from 0.73 to 2.52 AU. This data set is analyzed to determine the course of the production rate with heliocentric distance for C2, NH2, CN, and the

U. Fink

1994-01-01

51

Catalogue of video meteor orbits. Part 1  

NASA Astrophysics Data System (ADS)

The catalogue of the heliocentric orbits of 817 meteors recorded within the double station program of the video observation of meteors at the Ond?ejov Observatory in years 1998 - 2001 is presented. The electronic version of the catalogue is available on http://www.asu.cas.cz/~meteor/catalogues/.

Koten, P.; Spurný, P.; Borovi?ka, J.; Stork, R.

52

Gravitational Interaction of Objects Moving in Intersecting Orbits  

Microsoft Academic Search

The evolution of two, three, and one hundred gravitating objects, i.e., material points moving around the Sun in crossing orbits, is investigated numerically, mainly by the action spheres method. It is demonstrated that in the case of three identical objects, maximum eccentricities can exceed those for two like objects by a factor of several tens. Eccentricities of heliocentric orbits of

S. I. Ipatov

1995-01-01

53

Impactors on Saturn's Regular Satellites: Heliocentric vs. Planetocentric  

NASA Astrophysics Data System (ADS)

Voyager-era scientists concluded that Saturn's moons were struck by at least two impactor populations. Population I impactors - most likely "comets" orbiting the Sun - formed most of the larger and older craters, while Population II impactors - possibly Saturn-orbiting ejecta from impacts on satellites - produced most of the smaller and younger craters [1]. Present-day dynamical models predict that "ecliptic comets," which likely originate in the Kuiper Belt/Scattered Disk, are the primary impactors on the regular satellites of the giant planets [2]. However, these models predict vastly more craters on the leading faces of synchronously rotating moons than on the trailing faces [3]; such asymmetries are not observed. The answer to this riddle might be nonsynchronous rotation; crater saturation; or the putative Population II impactors, which should not create strong asymmetries [4]. We focus on Cassini measurements and interpretation of the crater size-frequency distributions on Mimas, Enceladus, and Rhea. Because Mimas and Enceladus have weak gravities, they are excellent sources of Saturn-orbiting ejecta, which usually come back to strike their parent moons, making "sesquinary" craters. Impacts on weightier Rhea are more apt to make traditional secondary craters [5]. We will apply ejecta models [6] to quantify the importance of sesquinary craters on the saturnian moons. The biggest uncertainty is the size of the ejecta [7]. We thank the CDAP program for support. References: [1] Dones L., et al., in Saturn from Cassini-Huygens, pp. 613-635 (2009). [2] Zahnle K., et al., Icarus 163, 263-289 (2003). [3] Zahnle K. et al., Icarus 153, 111-129 (2001). [4] Alvarellos J., et al., Icarus 178, 104-123. [5] Bierhaus E. et al., Lunar Planet. Sci. 42 (2011). [6] Housen K.R., Holsapple, K.A., Icarus 211, 856-875 (2011). [7] Zahnle K. et al., Icarus 194, 660-674 (2008).

Dones, Henry C. Luke; Bierhaus, E. B.; Zahnle, K. J.; Alvarellos, J. L.

2011-04-01

54

THE DISTRIBUTION OF QUIET-SUN MAGNETIC FIELDS AT DIFFERENT HELIOCENTRIC ANGLES  

SciTech Connect

This paper presents results from the analysis of high signal-to-noise ratio spectropolarimetric data taken at four heliocentric angles in quiet-Sun internetwork regions with the Hinode satellite. First, we find that the total circular and total linear polarization signals vary with heliocentric angle, at least for fields with large polarization signals. We also report changes on the Stokes V amplitude asymmetry histograms with viewing angle for fields weaker than 200 G. Then, we subject the data to a Milne-Eddington inversion and analyze the variation of the field vector probability density functions with heliocentric angle. Weak, highly inclined fields permeate the internetwork at all heliocentric distances. For fields weaker than 200 G, the distributions of field inclinations peak at 90 Degree-Sign and do not vary with viewing angle. The inclination distributions change for fields stronger than 200 G. We argue that the shape of the inclination distribution for weak fields partly results from the presence of coherent, loop-like magnetic features at all heliocentric distances and not from tangled fields within the field of view. We also find that the average magnetic field strength is about 180 G (for 75% of the pixels) and is constant with heliocentric angle. The average vertical and horizontal magnetic field components are 70 and 150 G. The latter (former) is slightly greater (smaller) near the limb. Finally, the ratio between the horizontal and vertical components of the fields ranges from {approx}1 for strong fields to {approx}3.5 for weak fields, suggesting that the magnetic field vector is not isotropically distributed within the field of view.

Orozco Suarez, D.; Katsukawa, Y., E-mail: d.orozco@nao.ac.jp [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2012-02-20

55

ICARUS 92, 118-131 (1991) Orbital Stability Zones about Asteroids  

E-print Network

be considered. If this is the case, the danger of collision with orbiting debris may increase as the asteroidICARUS 92, 118-131 (1991) Orbital Stability Zones about Asteroids DOUGLAS P. HAMILTON AND JOSEPH A properties: a circular heliocentric orbit at R -- 2.55 AU, an asteroid/Sun mass ratio of/~ -- 5 x 10

Hamilton, Douglas P.

56

Hyperbolic Orbits in the EDMOND  

NASA Astrophysics Data System (ADS)

The present work is based on an analysis of 83369 meteor orbits collected in the European video meteor network database - EDMOND (Kornoš et al. 2013a), 5.7% of which have orbits determined as hyperbolic. Among them, we searched for gravitationally accelerated meteoroids. The investigation showed that only 8 meteoroids from all 4712 hyperbolic orbits had close encounters with one of the major planets, giving a proportion of only 0.0017 of all hyperbolic orbits. However, for none of these 8 meteoroids did the integration procedure show significant changes in their orbits; thus, the close encounters did not cause their hyperbolicity. Indeed, our analysis showed that erroneous determinations of the heliocentric velocity is responsible for the vast majority of hyperbolic orbits among the detected meteors in the EDMOND.

Hajduková, M., Jr.; Kornoš, L.; Tóth, J.

2014-07-01

57

Heliocentric distance and temporal dependence of the interplanetary density-magnetic field magnitude correlation  

NASA Technical Reports Server (NTRS)

The Helios, IMP 8, ISEE 3, ad Voyager 2 spacecraft are used to examine the solar cycle and heliocentric distance dependence of the correlation between density n and magnetic field magnitude B in the solar wind. Previous work had suggested that this correlation becomes progressively more negative with heliocentric distance out to 9.5 AU. Here it is shown that this evolution is not a solar cycle effect, and that the correlations become even more strongly negative at heliocentric distance larger than 9.5 AU. There is considerable variability in the distributions of the correlations at a given heliocentric distance, but this is not simply related to the solar cycle. Examination of the evolution of correlations between density and speed suggest that most of the structures responsible for evolution in the anticorrelation between n and B are not slow-mode waves, but rather pressure balance structures. The latter consist of both coherent structures such as tangential discontinuities and the more generally pervasive 'pseudosound' which may include the coherent structures as a subset.

Roberts, D. A.

1990-01-01

58

Narrowband Photometry of Comet P\\/Halley: Variation with Heliocentric Distance, Season, and Solar Phase Angle  

Microsoft Academic Search

Narrowband filter photometry of Comet P\\/Halley from 109 nights in 1985, 1986, and 1987 is analyzed to discern the comet's variation in activity with changing heliocentric distance and season. The scattering phase function of dust in the coma is also investigated. Asymmetry about perihelion in the production of gas and dust is confirmed. However, we find the asymmetry to be

David G. Schleicher; Robert L. Millis; Peter V. Birch

1998-01-01

59

Pioneer and voyager observations of the solar wind at large heliocentric distances and lattitudes  

Microsoft Academic Search

The Pioneer 10, 11, and Voyager 2 spacecraft are well suited for exploring spatial gradients in the distant solar wind. Between 1984 and 1986 Pioneer 11 and Voyager 2 were located at nearly the same heliocentric distance (approx. =20 AU) and longitude but were widely separated in latitude; Pioneer 11 was at a heliographic latitude of greater than or equal

P. R. Gazis; J. D. Mihalov; A. Barnes; A. J. Lazarus; E. J. Smith

1989-01-01

60

On the gradients of ACR oxygen at intermediate heliocentric distances: Ulysses\\/SOHO results  

Microsoft Academic Search

During 1997 and up to the present time, the heliocentric position of the Ulysses spacecraft has changed only slowly in distance and latitude, being close to the equator at a distance of ?5 AU. This period provides an excellent opportunity to observe the evolution of the Anomalous Cosmic Ray (ACR) spectrum at a location intermediate between 1 AU and the

R. G Marsden; T. R Sanderson; C. Tranquille; K. J Trattner; A. Anttila; J. Torsti

1999-01-01

61

Solar wind structure at large heliocentric distances: An interpretation of Pioneer 10 observations  

Microsoft Academic Search

Examination of hourly values of the solar wind speed observed by the Pioneer 10 spacecraft beyond a heliocentric distance of 4 AU reveals (1) a prevalent 'sawtoothlike' speed-time profile, most speed fluctuations displaying a rapid rise and a much slower decline, and (2) the nearly universal appearance of abrupt (on the 1-hour time resolution of these data) changes in the

A. J. Hundhausen; J. T. Gosling

1976-01-01

62

Pioneer 10 observations of zodiacal light brightness near the ecliptic: Changes with heliocentric distance  

Microsoft Academic Search

Sky maps made by the Pioneer 10 Imaging Photopolarimeter (IPP) at sun-spacecraft distances from 1 to 3 AU have been analyzed to derive the brightness of the zodiacal light near the ecliptic at elongations greater than 90 degrees.The change in zodiacal light brightness with heliocentric distance is compared with models of the spatial distribution of the dust. Use of background

M. So HANNER; J. Go SPARROW; J. L. WEINBERG; D. Eo BEESON

63

The amplitudes of interplanetary fluctuations: Stream structure, heliocentric distance, and frequency dependence  

Microsoft Academic Search

The authors present a study of the heliocentric distance, frequency, and stream structure dependence of the amplitudes of interplanetary fluctuations in the velocity and magnetic field from 0.3 to nearly 20 AU and for spacecraft-frame periods of 10 days to a few hours. The results constrain theories of the acceleration of the solar wind and of the evolution of fluctuation

D. A. Roberts; M. L. Goldstein; L. W. Klein

1990-01-01

64

The possible formation of a hydrogen coma around comets at large heliocentric distances  

Microsoft Academic Search

An observational test, the detection of a hydrogen coma around comets at large heliocentric distances, is proposed for determining whether comets were formed by the agglomeration of unaltered, ice-coated, interstellar grains. Laboratory experiments showed that amorphous water ice traps H2, D2, and Ne below 20 K and does not release them completely until the ice is heated to 150 K.

A. Bar-Nun; D. Prialnik

1988-01-01

65

On the brightness variations of comet Halley at large heliocentric distances  

Microsoft Academic Search

Sporadic variations of its intrinsic brightness of up to 500%, with time scales as short as a few hours, has been exhibited by Halley's comet at large heliocentric distances (11-8 AU). It is shown that many of these brightness enhancements are closely correlated to the encounter of high-speed solar wind streams by the comet. It is proposed that during such

K. R. Flammer; B. Jackson; D. A. Mendis

1986-01-01

66

The trend of production rates with heliocentric distance for comet P/Halley  

NASA Astrophysics Data System (ADS)

Comet P/Halley was observed spectroscopically in the wavelength range 5200-10,400 A during 10 observing runs, roughly a month apart from 1985 August 28 to 1986 June 6. The observations span a heliocentric distance from 0.73 to 2.52 AU. This data set is analyzed to determine the course of the production rate with heliocentric distance for C2, NH2, CN, and the continuum. The effect of changing the Haser scale lengths and their heliocentric distance dependence is examined. The production rate ratios to water change only in a minor way, but the absolute values of the production rates are more severely affected. Fluorescent efficiencies, or g-factors for the CN red system are calculated, and band intensity ratios for NH2 and CN are presented. Using presently available fluorescence efficiencies and Haser scale lengths, mixing ratios for the parents of C2, CN, and NH2 with respect to water are: 0.34 +/- 0.07%, 0.15 +/- 0.04%, and 0.13 +/- 0.05%. It is found that these mixing ratios are essentially constant over the heliocentric distance range of the observations, implying a rather uniform nucleus and uniform outgassing characteristics, although there are indications of smaller scale day-to-day variations. The results provide strong observational confirmation that water evaporation controls the activity of the comet over the distance range studied. Continuum values Af rho are determined, and their ratios to QH2O are found to have a clear dependence with heliocentric distance approximately r-1.0 with a post-perihelion enhancement. No correlation of the production rate ratios with light curve of P/Halley were found, nor was there any correlation of the C2 or CN production with the dust.

Fink, U.

1994-03-01

67

The Kepler Mission: A wide-field transit search for terrestrial planets  

Microsoft Academic Search

The Kepler Mission is a NASA Discovery mission which will continuously monitor the brightness of at least 100,000 main sequence stars, to detect the transits of terrestrial and larger planets. It is scheduled to be launched in 2007 into an Earth-trailing heliocentric orbit. It is a wide-field photometer with a Schmidt-type telescope and array of 42 CCDs covering the 100

Gibor Basri; William J. Borucki; David Koch

2005-01-01

68

Galactic cosmic-ray intensity to a heliocentric distance of 18 AU  

NASA Technical Reports Server (NTRS)

The paper reports observations to heliocentric radial distances of 8.6 and 18.4 AU with Pioneer 11 and Pioneer 10 respectively. During a seven year period from March 1972 to March 1979, the galactic cosmic-ray intensity of greater than 80 MeV, as measured by detectors on Pioneers 10 and 11, exhibited aperiodic temporal variations by about a factor of 2 and on a time scale of the order of a year, and quasipersistent cyclic variations of a 26 day period and an amplitude of a few percent. For protons of an energy greater than 80 MeV, there is a fairly consistent heliocentric radial gradient of +2.1 (plus or minus 0.3%) per AU in integral intensity until 1978 April-May, at which time a substantial disruption of the distribution of cosmic rays in the heliosphere occurred.

Van Allen, J. A.

1980-01-01

69

Effect of a drag force due to absorption of solar radiation on solar sail orbital dynamics  

NASA Astrophysics Data System (ADS)

While solar electromagnetic radiation can be used to propel a solar sail, it is shown that the Poynting-Robertson effect related to the absorbed portion of the radiation leads to a drag force in the transversal direction. The Poynting-Robertson effect is considered for escape trajectories, Heliocentric bound orbits and non-Keplerian bound orbits. For escape trajectories, this drag force diminishes the cruising velocity, which has a cumulative effect on the Heliocentric distance. For Heliocentric and non-Keplerian bound orbits, the Poynting-Robertson effect decreases its orbital speed, thereby causing it to slowly spiral towards the Sun. Since the Poynting-Robertson effect is due to the absorbed portion of the electromagnetic radiation, degradation of a solar sail implies that this effect becomes enhanced during a mission.

Kezerashvili, Roman Ya.; Vázquez-Poritz, Justin F.

2013-03-01

70

Observed and real orbital dispersion within meteoroid streams  

NASA Astrophysics Data System (ADS)

The present paper, based on a statistical analysis of orbits obtained from video meteors, shows the orbits' distribution within the meteoroid streams with heliocentric velocities close to the parabolic limit. The high proportion of hyperbolic orbits among the corresponding meteor showers was used to deduce the contribution of the real orbital dispersion within the stream, because an excess of a heliocentric velocity of a stream meteoroid over the parabolic value can be regarded entirely as the result of measuring errors. Four meteor showers, April Lyrids, Perseids, Orionids, and Leonids, were selected for this analysis. The orbital dispersion within the investigated meteoroid streams, based on the distribution of their reciprocal semimajor axes, obtained from different catalogues, were compared. It was shown that the major part of the observed differences in the semimajor axes within meteoroid streams from the European Video Meteor Network data is indeed due to measuring errors.

Hajduková, Mária

2014-01-01

71

On the Provability of Heliocentrism. II. Leon Foucault and the Rotation of the Earth  

NASA Astrophysics Data System (ADS)

This paper deals with the experimental provability of heliocentrism from the scientific Renaissance in the beginning of the 17th century, till the Industrial Revolution of the 1850s. Foucault's famous pendulum demonstration is documented. We underline the importance of high accuracy of observations, the interdependence of hypotheses and theories, the impact of technological breakthroughs, the role of serendipity, the importance of fast and accurate publishing, and the need for precise science communication and teaching.

Sterken, Christiaan

2007-10-01

72

Heliocentric Dependence of the Sodium Emission of Comet 153P\\/Ikeya-Zhang  

Microsoft Academic Search

A low-dispersion spectroscopic monitor of comet 153P\\/Ikeya-Zhang was carried out from 2002 February through May. The sodium emission was derived mainly during March, when the heliocentric distance of the comet was between 0.511 and 0.764 AU. The number of the produced sodium atoms relative to the total cross section of dust grains follows a power law of r-5.1+\\/-1.0, where r

Jun-ichi Watanabe; Hideyo Kawakita; Reiko Furusho; Mitsugu Fujii

2003-01-01

73

Comet 67P\\/Churyumov-Gerasimenko at a large heliocentric distance  

Microsoft Academic Search

Aims: The Jupiter family comet 67P\\/Churyumov-Gerasimenko (67P\\/C-G) is the target comet of ESA's ROSETTA mission. A detailed portrait of this comet has been drawn from observations around perihelion, but what needs to be enhanced is the description of the comet's behaviour at large heliocentric distance. It is not only important for planning the rendezvous of the ROSETTA spacecraft with the

C. Tubiana; L. Barrera; M. Drahus; H. Boehnhardt

2008-01-01

74

Antarctic polar plateau vertical electric field variations across heliocentric current sheet crossings  

Microsoft Academic Search

A superposed epoch analysis of variations of the vertical electric field measured at Vostok (78.5°S, 107°E; magnetic latitude 83.6°S) during 1998–2002 heliocentric current sheet (HCS) crossings yields no significant variation other than an association imposed by polar-cap potential differences above the site. This result contradicts published reports of a reduction ?15% in electric field 1–3 days after HCS crossings, an

G. B. Burns; B. A. Tinsley; A. R. Klekociuk; O. A. Troshichev; A. V. Frank-Kamenetsky; M. L. Duldig; E. A. Bering; J. M. Clem

2006-01-01

75

Near-IR internetwork spectro-polarimetry at different heliocentric angles  

Microsoft Academic Search

The analysis of near infrared spectropolarimetric data at the internetwork at\\u000adifferent regions on the solar surface could offer constraints to reject\\u000acurrent modeling of these quiet areas.\\u000a We present spectro-polarimetric observations of very quiet regions for\\u000adifferent values of the heliocentric angle for the Fe I lines at 1.56 micron,\\u000afrom disc centre to positions close to the limb.

M. Jesus Martinez Gonzalez; A. Asensio Ramos; A. Lopez Ariste; R. Manso Sainz

2007-01-01

76

Constraining the Dust Coma Properties of Comet C/Siding Spring (2013 a1) at Large Heliocentric Distances  

NASA Astrophysics Data System (ADS)

The close encounter of comet C/2013 A1 (Siding Spring) with Mars on 2014 October 19 presented an extremely rare opportunity to obtain the first flyby quality data of the nucleus and inner coma of a dynamically new comet. However, the comet's dust tail potentially posed an impact hazard to those spacecraft orbiting Mars. To characterize the comet at large heliocentric distances, study its long-term evolution, and provide critical inputs to hazard modeling, we imaged C/Siding Spring with the Hubble Space Telescope when the comet was at 4.58, 3.77, and 3.28 AU from the Sun. The dust production rate, parameterized by the quantity Af?, was 2500, 2100, and 1700 cm (5000 km radius aperture) for the three epochs, respectively. The color of the dust coma is (5.0 ± 0.3)%/100 nm for the first two epochs, and (9.0 ± 0.3)%/100 nm for the last epoch, and reddens with increasing cometocentric distance out to ~3000 km from the nucleus. The spatial distribution and the temporal evolution of the dust color are most consistent with the existence of icy grains in the coma. Two jet-like dust features appear in the northwest and south-southeast directions projected in the sky plane. Within each epoch of 1-2 hr, no temporal variations were observed for either feature, but the position angle of the south-southeastern feature varied between the three epochs by ~30°. The dust feature morphology suggests two possible orientations for the rotational pole of the nucleus, (R.A., decl.) = (295° ± 5°, +43° ± 2°) and (190° ± 10°, +50° ± 5°), or their diametrically opposite orientations.

Li, Jian-Yang; Samarasinha, Nalin H.; Kelley, Michael S. P.; Farnham, Tony L.; A'Hearn, Michael F.; Mutchler, Max J.; Lisse, Carey M.; Delamere, W. Alan

2014-12-01

77

A Numerical Study of Comet Mcnaught over a Wide Range of Heliocentric Distances  

NASA Astrophysics Data System (ADS)

A numerical study of Comet McNaught over a wide range of heliocentric distances Yinsi Shou, Michael R. Combi, Martin Rubin, Gabor Toth The Comet C/2006 P1 (McNaught) has a small perihelion distance (0.17 AU) and had a very high production rate during its passage close to the Sun in January and February of 2007. During that period, it was monitored by both ground- and space-based observatories, which provided substantial information about the comet. In early February, the Ulysses spacecraft encountered its ion tail and gave clues to the surrounding solar wind conditions and to the cometary environment. Therefore, Comet McNaught is an ideal object to study the cometary structures under extreme conditions and the solar wind-comet interaction over a wide range of heliocentric distances. A numerical study of Comet McNaught combining two models is conducted. First, a single species magnetohydrodynamics (MHD) [Gombosi et al. (1996, JGR 101, 15233)] simulation is performed using a set of ‘observed’ comet parameters as input. Then a chemistry model [Häberli et al. (1997, Icarus 130, 373)] extracts the streamlines from the MHD model and calculates the densities of different species accounting for photo-dissociation, photo-ionization, electron recombination, ion-molecule and charge-exchange reactions. The MHD results are able to give the diamagnetic cavity sizes and shock distances at various heliocentric distances while the chemistry model better resolves the distribution of the major chemical species in the cometary plasma environment. The combination of the two models allows us to obtain detailed information on the chemical composition of a much wider range of atoms and molecules compared to multi-species or multi-fluid MHD models and at much lower computational expense. Some preliminary results are presented and discussed. This work has been partially supported by grant AST-0707283 from the NSF Planetary Astronomy program and NASA Planetary Atmospheres program grant NNX09AB59G.

Shou, Yinsi; Combi, M. R.; Rubin, M.; Toth, G.

2012-10-01

78

Sublimation rates of carbon monoxide and carbon dioxide from comets at large heliocentric distances  

NASA Technical Reports Server (NTRS)

Using a simple model for outgassing from a small flat surface area, the sublimation rates of carbon monoxide and carbon dioxide, two species more volatile than water ice that are known to be present in comets, are calculated for a suddenly activated discrete source on the rotating nucleus. The instantaneous sublimation rate depends upon the comet's heliocentric distance and the Sun's zenith angle at the location of the source. The values are derived for the constants of CO and CO2 in an expression that yields the local rotation-averaged sublimation rate as a function of the comet's spin parameters and the source's cometocentric latitude.

Sekanina, Zdenek

1992-01-01

79

Near-IR internetwork spectro-polarimetry at different heliocentric angles  

E-print Network

The analysis of near infrared spectropolarimetric data at the internetwork at different regions on the solar surface could offer constraints to reject current modeling of these quiet areas. We present spectro-polarimetric observations of very quiet regions for different values of the heliocentric angle for the Fe I lines at 1.56 micron, from disc centre to positions close to the limb. The spatial resolution of the data is 0.7-1". We analyze direct observable properties of the Stokes profiles as the amplitude of circular and linear polarization as well as the total degree of polarization. Also the area and amplitude asymmetries are studied. We do not find any significant variation of the properties of the polarimetric signals with the heliocentric angle. This means that the magnetism of the solar internetwork remains the same regardless of the position on the solar disc. This observational fact discards the possibility of modeling the internetwork as a Network-like scenario. The magnetic elements of internetwork areas seem to be isotropically distributed when observed at our spatial resolution.

M. Jesus Martinez Gonzalez; A. Asensio Ramos; A. Lopez Ariste; R. Manso Sainz

2007-10-27

80

Complex of meteoroid orbits with high eccentricities  

NASA Astrophysics Data System (ADS)

In our work is demonstrated the method that can help to predict the existence of distant objects in the Solar system. This method is connected with statistical properties of a heliocentric orbital complex of meteoroids with high eccentricities. Heliocentric meteoroid orbits with high eccentricities are escape routes for dust material from distant parental objects with near-circular orbits to Earth-crossing orbits. Ground-based meteor observations yield trajectory information from which we can derive their place of possible origin: comets asteroids and other objects (e.g. Kuiper Objects) in the Solar system or even interstellar space [12]. Such information is important at planning space missions. We analyze elliptic meteor orbits with high eccentricities that were registered in 1972 - 1978 in Kharkiv (Ukraine). Statistical distributions of radius-vectors of nodes and aphelia of orbits of meteoroids contain key information about position of greater bodies. We discuss the accuracy of the ground-based radar observations of faint meteors. An estimation of selectivity factors of meteor radar measurements is made on base of radiophysical and astronomical researches of meteoric substance and its interaction atmosphere of the Earth. [1] S. Kolomiyets (2002) Abstracts ACM 2002 Berlin 37. [2] B. Kashcheyev S. Kolomiyets (2001) SP-495 643.

Kolomiyets, Svitlana V.; Kashcheyev, Boris L.

2005-01-01

81

Possible Periodic Orbit Control Maneuvers for an eLISA Mission  

NASA Astrophysics Data System (ADS)

This paper investigates the possible application of periodic orbit control maneuvers for so-called evolved-LISA (eLISA) missions, i.e., missions for which the constellation arm lengths and mean distance from the Earth are substantially reduced. We find that for missions with arm lengths of ˜ 106 km and Earth-trailing distance ranging from ˜ 12° to 20° over the science lifetime, the occasional use of the spacecraft micro-Newton thrusters for constellation configuration maintenance should be able to essentially eliminate constellation distortion caused by Earth-induced tidal forces at a cost to science time of only a few percent. With interior angle variation kept to ˜ ± 0.1°, the required changes in the angles between the laser beam pointing directions for the two arms from any spacecraft could be kept quite small. This would considerably simplify the apparatus necessary for changing the transmitted beam directions.

Bender, P. L.; Welter, G. L.

2013-01-01

82

Possible Periodic Orbit Control Maneuvers for an eLISA Mission  

NASA Technical Reports Server (NTRS)

This paper investigates the possible application of periodic orbit control maneuvers for so-called evolved-LISA (eLISA) missions, i.e., missions for which the constellation arm lengths and mean distance from the Earth are substantially reduced. We find that for missions with arm lengths of 106 km and Earth-trailing distance ranging from approx. 12deg to 20deg over the science lifetime, the occasional use of the spacecraft micro-Newton thrusters for constellation configuration maintenance should be able to essentially eliminate constellation distortion caused by Earth-induced tidal forces at a cost to science time of only a few percent. With interior angle variation kept to approx. +/-0:1deg, the required changes in the angles between the laser beam pointing directions for the two arms from any spacecraft could be kept quite small. This would considerably simplify the apparatus necessary for changing the transmitted beam directions.

Bender, Peter L.; Welter, Gary L.

2012-01-01

83

The heliocentric evolution of cometary infrared spectra - Results from an organic grain model  

NASA Technical Reports Server (NTRS)

An emission feature peaking near 3.4 microns that is typical of C-H stretching in hydrocarbons and which fits a simple, two-component thermal emission model for dust in the cometary coma, has been noted in observations of Comets Halley and Wilson. A noteworthy consequence of this modeling is that, at about 1 AU, emission features at wavelengths longer than 3.4 microns come to be 'diluted' by continuum emission. A quantitative development of the model shows it to agree with observational data for Comet Halley for certain, plausible values of the optical constants; the observed heliocentric evolution of the 3.4-micron feature thereby furnishes information on the composition of the comet's organic grains.

Chyba, Christopher F.; Sagan, Carl; Mumma, Michael J.

1989-01-01

84

Gravity and Orbits: Orbits  

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:? Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.? Explain how an object orbits a planet in terms of trajectories and free fall.? Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2006-11-01

85

Telemetry coding study for the international magnetosphere explorers, mother/daughter and heliocentric missions. Volume 2: Final report  

NASA Technical Reports Server (NTRS)

A convolutional coding theory is given for the IME and the Heliocentric spacecraft. The amount of coding gain needed by the mission is determined. Recommendations are given for an encoder/decoder system to provide the gain along with an evaluation of the impact of the system on the space network in terms of costs and complexity.

Cartier, D. E.

1973-01-01

86

Fundamental and Harmonic Emission in Type III Solar Radio Bursts – III. Heliocentric Variation of Interplanetary Beam and Source Parameters  

Microsoft Academic Search

The parameters of type III solar radio sources have been observed to vary approximately as powers of the heliocentric distance. Recent theoretical studies of fundamental and harmonic emission are used to express the power-law exponents in terms of five basic ones. The results are then used to obtain a best fit to these five exponents, consistent with observed values of

P. A. Robinson; I. H. Cairns

1998-01-01

87

Characteristics of large Forbush-type decreases in the cosmic radiation 2. Observations at different heliocentric radial distances  

Microsoft Academic Search

Cosmic ray data from IMP 8, Voyager 1 and 2, Pioneer 10 are used to investigate the heliocentric radial dependence of the characteristics of about 20 Forbush-type transient decreases which occurred from 1978 to 1984. These characteristics include (1) the recovery time, (2) the amplitude, and (3) the time to decrease to minimum. It is found that the average recovery

W. R. Webber; J. A. Lockwood; J. R. Jokipii

1986-01-01

88

Domain analysis and information retrieval through the construction of heliocentric maps based on ISI-JCR category cocitation  

Microsoft Academic Search

We propose the use of ISI-JCR categories as units of cocitation and measurement for the construction of heliocentric maps. The use of a spatial metaphor allows us to illustrate, analyze and compare domains in terms of the categories and their interconnections or links. We can also move around within the structure of these domains for further analysis, and access the

Felix de Moya-Anegon; Benjamin Vargas-Quesada; Zaida Chinchilla-Rodriguez; Elena Corera-Alvarez; Victor Herrero-Solana; Francisco J. Munoz-Fernandez

89

Cosmic-ray exposure age and heliocentric distance of the parent bodies of enstatite chondrites ALH 85119 and MAC 88136  

Microsoft Academic Search

We measured concentrations and isotopic ratios of noble gases in enstatite (E) chondrites Allan Hills (ALH) 85119 and MacAlpine Hills (MAC) 88136. These two meteorites contain solar and cosmogenic noble gases. Based on the solar and cosmogenic noble gas compositions, we calculated heliocentric distances, parent body exposure ages, and space exposure ages of the two meteorites. The parent body exposure

D. Nakashima; T. Nakamura; R. Okazaki

2006-01-01

90

A Synoptic Analysis of the Change from the Geocentric to the Heliocentric Conception of the Solar System.  

ERIC Educational Resources Information Center

The changes which occurred in man's view of the solar system from the time of Ptolemy to that of Galileo are presented. Contained is a brief review of the chain of events which resulted in the acceptance of a heliocentric system. Ptolomy's theory is described and a diagram illustrates the paths of the epicycle of Mars according to his geocentric…

Wilson, Roosevelt L.

91

Orbit Determination and Navigation of the Solar Terrestrial Relations Observatory (STEREO)  

NASA Technical Reports Server (NTRS)

This paper provides an overview of the required upgrades necessary for navigation of NASA's twin heliocentric science missions, Solar TErestrial RElations Observatory (STEREO) Ahead and Behind. The orbit determination of the STEREO spacecraft was provided by the NASA Goddard Space Flight Center's (GSFC) Flight Dynamics Facility (FDF) in support of the mission operations activities performed by the Johns Hopkins University Applied Physics Laboratory (APL). The changes to FDF's orbit determination software included modeling upgrades as well as modifications required to process the Deep Space Network X-band tracking data used for STEREO. Orbit results as well as comparisons to independently computed solutions are also included. The successful orbit determination support aided in maneuvering the STEREO spacecraft, launched on October 26, 2006 (00:52 Z), to target the lunar gravity assists required to place the spacecraft into their final heliocentric drift-away orbits where they are providing stereo imaging of the Sun.

Mesarch, Michael A.; Robertson, Mika; Ottenstein, Neil; Nicholson, Ann; Nicholson, Mark; Ward, Douglas T.; Cosgrove, Jennifer; German, Darla; Hendry, Stephen; Shaw, James

2007-01-01

92

Kepler Stars with Multiple Transiting Planet Candidates  

NASA Technical Reports Server (NTRS)

NASA's Kepler spacecraft was launched into an Earth-trailing heliocentric orbit in March of 2009. Kepler is designed to conduct a statistical census of planetary system properties using transit photometry. Among the most exciting early results from Kepler are target stars found to have photometric signatures that suggest the presence of more than one transiting planet. Individual transiting planets provide information on the size and orbital period distributions of exoplanets. Multiple transiting planets provide additional information on the spacing and flatness distributions of planetary systems. Results to d ate and plans for future analysis will be presented.

Lissauer, Jack J.

2012-01-01

93

Sailcraft at high speed by orbital angular momentum reversal  

Microsoft Academic Search

Considering a photon solar sail spacecraft with a lightness number (?) in the range [0.5-1) (all-metallic sails), this paper analyses a class of heliocentric trajectories, characterized by orbital angular-momentum reversal, delivering a considerable final spacecraft speed. It is found out that, if both the radial and transversal lightness numbers satisfy certain inequality constraints, the sailcraft in the solar gravitational field

Giovanni Vulpetti

1997-01-01

94

EVOLUTION OF CORONAL MASS EJECTION MORPHOLOGY WITH INCREASING HELIOCENTRIC DISTANCE. II. IN SITU OBSERVATIONS  

SciTech Connect

Interplanetary coronal mass ejections (ICMEs) are often observed to travel much faster than the ambient solar wind. If the relative speed between the two exceeds the fast magnetosonic velocity, then a shock wave will form. The Mach number and the shock standoff distance ahead of the ICME leading edge is measured to infer the vertical size of an ICME in a direction that is perpendicular to the solar wind flow. We analyze the shock standoff distance for 45 events varying between 0.5 AU and 5.5 AU in order to infer their physical dimensions. We find that the average ratio of the inferred vertical size to measured radial width, referred to as the aspect ratio, of an ICME is 2.8 {+-} 0.5. We also compare these results to the geometrical predictions from Paper I that forecast an aspect ratio between 3 and 6. The geometrical solution varies with heliocentric distance and appears to provide a theoretical maximum for the aspect ratio of ICMEs. The minimum aspect ratio appears to remain constant at 1 (i.e., a circular cross section) for all distances. These results suggest that possible distortions to the leading edge of ICMEs are frequent. But, these results may also indicate that the constants calculated in the empirical relationship correlating the different shock front need to be modified; or perhaps both distortions and a change in the empirical formulae are required.

Savani, N. P.; Kusano, K. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya (Japan); Owens, M. J. [Space Environment Physic Group, University of Reading, Reading (United Kingdom); Rouillard, A. P. [College of Science, George Mason University, Fairfax, VA (United States); Forsyth, R. J. [Blackett Laboratory, Imperial College London, London (United Kingdom); Shiota, D. [Computational Astrophysics Laboratory, Advanced Science Institute, RIKEN, Wako (Japan); Kataoka, R. [Interactive Research Center of Science, Tokyo Institute of Technology, Tokyo (Japan); Jian, L. [Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA (United States); Bothmer, V., E-mail: neel.savani02@imperial.ac.uk [Institut fuer Astrophysik, Goettingen University, Goettingen (Germany)

2011-05-10

95

Analysis of the interplanetary magnetic field observations at different heliocentric distances  

NASA Astrophysics Data System (ADS)

Multi-spacecraft measurements of the interplanetary magnetic field (IMF) from 0.29 AU to 5 AU along the ecliptic plane have demonstrated systematic deviations of the observed IMF strength from the values predicted on the basis of the Parker-like radial extension models (Khabarova, Obridko, 2012). In particular, it was found that the radial IMF component |Br| decreases with a heliocentric distance r with a slope of -5/3 (instead of r-2 expansion law). The current investigation of multi-point observations continues the analysis of the IMF (and, especially, Br) large-scale behaviour, including its latitudinal distribution. Additionally, examples of the mismatches between the expected IMF characteristics and observations at smaller scales are discussed. It is shown that the observed effects may be explained by not complete IMF freezing-in to the solar wind plasma. This research was supported by the Russian Fund of Basic Researches' grants Nos.11-02-00259-a, and 12-02-10008-K. Khabarova Olga, and Obridko Vladimir, Puzzles of the Interplanetary Magnetic Field in the Inner Heliosphere, 2012, Astrophysical Journal, 761, 2, 82, doi:10.1088/0004-637X/761/2/82, http://arxiv.org/pdf/1204.6672v2.pdf

Khabarova, Olga

2013-04-01

96

Photochemistry of atomic oxygen green and red-doublet emissions in comets at larger heliocentric distances  

E-print Network

In comets the atomic oxygen green to red-doublet emission intensity ratio (G/R ratio) of 0.1 has been used to confirm H$_2$O as the parent species producing oxygen emission lines. The larger ($>$0.1) value of G/R ratio observed in a few comets is ascribed to the presence of higher CO$_2$ and CO relative abundances in the cometary coma. We aim to study the effect of CO$_2$ and CO relative abundances on the observed G/R ratio in comets observed at large ($>$2 au) heliocentric distances by accounting for important production and loss processes of O($^1$S) and O($^1$D) in the cometary coma. Recently we have developed a coupled chemistry-emission model to study photochemistry of O($^1$S) and O($^1$D) atoms and the production of green and red-doublet emissions in comets Hyakutake and Hale-Bopp. In the present work we applied the model to six comets where green and red-doublet emissions are observed when they are beyond 2 au from the Sun. In a water-dominated cometary coma and with significant ($>$10%) CO$_2$ relati...

Raghuram, Susarla

2014-01-01

97

Heliocentric Potential (HCP) Prediction Model for Nowscast of Aviation Radiation Dose  

NASA Astrophysics Data System (ADS)

It is well known that the space radiation dose over the polar route should be carefully considered especially when the space weather shows sudden disturbances such as CME and flares. The National Meteorological Satellite Center (NMSC) and Korea Astronomy and Space Science Institute (KASI) recently established a basis for a space radiation service for the public by developing a space radiation prediction model and heliocentric potential (HCP) prediction model. The HCP value is used as a critical input value of the CARI-6 and CARI-6M programs, which estimate the aviation route dose. The CARI-6/6M is the most widely used and confidential program that is officially provided by the U.S. Federal Aviation Administration (FAA). The HCP value is given one month late in the FAA official webpage, making it difficult to obtain real-time information on the aviation route dose. In order to overcome this limitation regarding time delay, we developed a HCP prediction model based on the sunspot number variation. In this paper, we focus on the purpose and process of our HCP prediction model development. Finally, we find the highest correlation coefficient of 0.9 between the monthly sunspot number and the HCP value with an eight month time shift.

Hwang, Junga; Kim, Kyung-Chan; Dokgo, Kyunghwan; Choi, Enjin; Kim, Hang-Pyo

2015-03-01

98

Orbital evolution modeling of Damocloides  

NASA Astrophysics Data System (ADS)

In this paper we performed the task of orbital evolution modeling for 93 currently known Damocloids, 1 Gyr backward and forward in time, using the integration package SWIFTER. The package includes seven integration technics. We choosed the SyMBA integrator (Symplectic Massive Body Algorithm), which allows to handle close approaches between test particles and planets. We included the Sun, the eight planets, and Pluto as massive bodies in our simulation. The initial state vectors for test particles and planets were taken from HORIZONS JPL service. The timestep of integration was 7.305 days. The calculations were stopped when the particle reached heliocentric distance 5000 AU. The value is close to the inner boundary of the Oort cloud. It is shown, that dynamical lifetime of the population is about 1-10 myr. We present the Damocloids orbital parameters distributions and discuss the results of the simulation for Damocloids inclinations changes with time. Our results show that the dynamic lifetime of Damocloids population is about 106-107 years. Population of Damocloids retains highly inclined orbits during the integration time into the past and into the future. Thus, the population of Damocloids may indeed represent the dynamical relationship of comets on inclined orbits (Halley-type comets) with a hypothetical spherical Oort Cloud. Some of evolutionary tracks allow transition from retrograde motion to direct and vice versa (e.g.Dioretsa asteroid (20461)). However, for large periods of time, due to close encounters with the giant planets, the simulation results should be considered only statistically.

Guliyev, Rustam; Churyumov, Klim; Kovalenko, Nataliya

99

Data catalog series for space science and applications flight missions. Volume 1A: Brief descriptions of planetary and heliocentric spacecraft and investigations  

NASA Technical Reports Server (NTRS)

Planetary and heliocentric spacecraft, including planetary flybys and probes, are described. Imaging, particles and fields, ultraviolet, infrared, radio science and celestial mechanics, atmospheres, surface chemistry, biology, and polarization are discussed.

Cameron, W. S. (editor); Vostreys, R. W. (editor)

1982-01-01

100

Orbital pseudotumor  

MedlinePLUS

Orbital pseudotumor is a swelling of the tissues behind the eye in an area called the orbit. The ... and tissue that surround it. Unlike cancerous tumors, orbital pseudotumor does not spread to other tissues or places ...

101

Extrasolar Planetary Imaging Coronagraph (EPIC)  

NASA Technical Reports Server (NTRS)

EPIC is a NASA mission being studied to detect and characterize Jovian and superEarth planets, and, the dust/debris disks surrounding the parent star. It will be launched into a heliocentric Earth trailing orbit and operate for 5 years. EPIC would operate over the wavelength range of 480 - 960 nm with spectral resolutions of R < 50 and employs a visible nulling coronagraph (VNC) to suppress the starlight, yielding contrast ratios of greater than 9 orders of magnitude. We will discuss the science mission, and its role in the search for habitable planets.

Clampin, Mark

2009-01-01

102

Contingency Trajectory Design for a Lunar Orbit Insertion Maneuver Failure by the Lunar Atmosphere Dust Environment Explorer (LADEE) Spacecraft  

NASA Technical Reports Server (NTRS)

The purpose of this extended abstract is to present results from a failed lunar-orbit insertion (LOI) maneuver contingency analysis for the Lunar Atmosphere Dust Environment Explorer (LADEE) mission, managed and operated by NASA Ames Research Center in Moffett Field, CA. The LADEE spacecrafts nominal trajectory implemented multiple sub-lunar phasing orbits centered at Earth before eventually reaching the Moon (Fig. 1) where a critical LOI maneuver was to be performed [1,2,3]. If this LOI was missed, the LADEE spacecraft would be on an Earth-escape trajectory, bound for heliocentric space. Although a partial mission recovery is possible from a heliocentric orbit (to be discussed in the full paper), it was found that an escape-prevention maneuver could be performed several days after a hypothetical LOI-miss, allowing a return to the desired science orbit around the Moon without leaving the Earths sphere-of-influence (SOI).

Genova, Anthony L.; Loucks, Michael; Carrico, John

2014-01-01

103

Photochemistry of atomic oxygen green and red-doublet emissions in comets at larger heliocentric distances  

NASA Astrophysics Data System (ADS)

Context. In comets, the atomic oxygen green (5577 Å) to red-doublet (6300, 6364 Å) emission intensity ratio (G/R ratio) of 0.1 has been used to confirm H2O as the parent species producing forbidden oxygen emission lines. The larger (>0.1) value of G/R ratio observed in a few comets is ascribed to the presence of higher CO2 and CO relative abundances in the cometary coma. Aims: We aim to study the effect of CO2 and CO relative abundances on the observed G/R ratio in comets observed at large (>2 au) heliocentric distances by accounting for important production and loss processes of O(1S) and O(1D) atoms in the cometary coma. Methods: Recently we have developed a coupled chemistry-emission model to study photochemistry of O(1S) and O(1D) atoms and the production of green and red-doublet emissions in comets Hyakutake and Hale-Bopp. In the present work we applied the model to six comets where green and red-doublet emissions are observed when they are beyond 2 au from the Sun. Results: The collisional quenching of O(1S) and O(1D) can alter the G/R ratio more significantly than that due to change in the relative abundances of CO2 and CO. In a water-dominated cometary coma and with significant (>10%) CO2 relative abundance, photodissociation of H2O mainly governs the red-doublet emission, whereas CO2 controls the green line emission. If a comet has equal composition of CO2 and H2O, then ~50% of red-doublet emission intensity is controlled by the photodissociation of CO2. The role of CO photodissociation is insignificant in producing both green and red-doublet emission lines and consequently in determining the G/R ratio. Involvement of multiple production sources in the O(1S) formation may be the reason for the observed higher green line width than that of red lines. The G/R ratio values and green and red-doublet line widths calculated by the model are consistent with the observation. Conclusions: Our model calculations suggest that in low gas production rate comets the G/R ratio greater than 0.1 can be used to constrain the upper limit of CO2 relative abundance provided the slit-projected area on the coma is larger than the collisional zone. If a comet has equal abundances of CO2 and H2O, then the red-doublet emission is significantly (~50%) controlled by CO2 photodissociation and thus the G/R ratio is not suitable for estimating CO2 relative abundance.

Raghuram, Susarla; Bhardwaj, Anil

2014-06-01

104

Organic ices in the coma of comet C/2012 S1 (ISON) at heliocentric distances greater than 4 AU?  

NASA Astrophysics Data System (ADS)

Comet C/2012 S1 (ISON) was monitored during its approach to the inner solar system, when the comet passed from a heliocentric distance of 6.0 to 4.3 AU. As many other Oort cloud comets at their first approach to the Sun, also comet ISON exhibited a systematic over population of grains in the inner part of the coma, as revealed by the ?Af function (Tozzi et al., 2007, A&A 476, 979). So far this effect has been interpreted as due either to a short timescale variation of activity (outbursts), or long timescale variation of activity associated with very low escape velocity of the grains or with sublimating grains. In the presentation we will show that the most likely explanation of the phenomena is the sublimation of icy CO2 grains. We will discuss also the implication of CO2 production rates by this distributed source on the whole gas production rates of the comet at so large heliocentric distances.

Tozzi, Gian-Paolo; Faggi, Sara; Brucato, John R.; Bruni, Ivan; Licandro, Javier; Mazzotta Epifani, Elena; Meech, Karen; Mottola, Stefano; Watanabe, Makoto

2014-11-01

105

A Dynamical Analysis of the Dust Tail of Comet C/1995 O1 (Hale-Bopp) at High Heliocentric Distances  

E-print Network

Comet C/1995 O1 (Hale-Bopp) has provided an unprecedented opportunity to observe a bright comet over a wide range of heliocentric distances. We present here Spitzer Space Telescope observations of Hale-Bopp from 2005 and 2008 that show a distinct coma and tail, the presence of which is uncommon given its large heliocentric distance (21.6 AU and 27.2 AU, respectively). The morphology of the dust is compared to dynamical models to understand the activity of the comet. Our analysis shows that the shape of Hale-Bopp's dust tail in these images cannot be explained using the usual Finson-Probstein (solar gravity + solar radiation pressure) dynamical model. Several alternative explanations are explored. The analysis suggests that the most likely cause of the discrepancy is that the dust is being charged by the solar wind, then being affected by the interplanetary magnetic field via the Lorentz force. Though this effect has been explored previously, if correct, this seems to be the first time that the Lorentz force h...

Kramer, Emily A; Lisse, Carey M; Kelley, Michael S; Woodney, Laura M

2014-01-01

106

Orbital Decompression  

MedlinePLUS

INTRODUCTION Orbital decompression is a surgical procedure which has been in existence for well over 100 years to treat a variety ... optic nerve) and fat). The goal of orbital decompression is to remove some of the bony walls ...

107

Program manual for HILTOP, a heliocentric interplanetary low thrust trajectory optimization program. Part 1: User's guide  

NASA Technical Reports Server (NTRS)

A performance-analysis computer program, that was developed explicitly to generate optimum electric propulsion trajectory data for missions of interest in the exploration of the solar system is presented. The program was primarily designed to evaluate the performance capabilities of electric propulsion systems, and in the simulation of a wide variety of interplanetary missions. A numerical integration of the two-body, three-dimensional equations of motion and the Euler-Lagrange equations was used in the program. Transversality conditions which permit the rapid generation of converged maximum-payload trajectory data, and the optimization of numerous other performance indices for which no transversality conditions exist are included. The ability to simulate constrained optimum solutions, including trajectories having specified propulsion time and constant thrust cone angle, is also in the program. The program was designed to handle multiple-target missions with various types of encounters, such as rendezvous, stopover, orbital capture, and flyby. Performance requirements for a variety of launch vehicles can be determined.

Mann, F. I.; Horsewood, J. L.

1974-01-01

108

Heliocentric radial intensity profiles of galactic cosmic rays measured by the IMP, Voyager, and Pioneer spacecraft in solar 11-year modulation cycles of opposite magnetic polarity  

Microsoft Academic Search

We examine in this paper the heliocentric radial intensity profiles at heliolatitudes <35° of five energies\\/species of galactic cosmic rays as measured by IMP, Pioneer 10, and Voyagers 1 and 2 over several 11-year solar cycles of different solar magnetic polarity. At times of maximum solar modulation the radial profiles in each cycle are remarkably similar. At times of minimum

W. R. Webber; J. A. Lockwood

2004-01-01

109

[Orbital inflammation].  

PubMed

Orbital inflammation is a generic term encompassing inflammatory pathologies affecting all structures within the orbit : anterior (involvement up to the posterior aspect of the globe), diffuse (involvement of intra- and/or extraconal fat), apical (involvement of the posterior orbit), myositis (involvement of only the extraocular muscles), dacryoadenitis (involvement of the lacrimal gland). We distinguish between specific inflammation and non-specific inflammation, commonly referred to as idiopathic inflammation. Specific orbital inflammation corresponds to a secondary localization of a "generalized" disease (systemic or auto-immune). Idiopathic orbital inflammation corresponds to uniquely orbital inflammation without generalized disease, and thus an unknown etiology. At the top of the differential diagnosis for specific or idiopathic orbital inflammation are malignant tumors, represented most commonly in the adult by lympho-proliferative syndromes and metastases. Treatment of specific orbital inflammation begins with treatment of the underlying disease. For idiopathic orbital inflammation, treatment (most often corticosteroids) is indicated above all in cases of visual loss due to optic neuropathy, in the presence of pain or oculomotor palsy. PMID:25455557

Mouriaux, F; Coffin-Pichonnet, S; Robert, P-Y; Abad, S; Martin-Silva, N

2014-12-01

110

Elliptical Orbits  

NSDL National Science Digital Library

This resource provides a textual explanation as well as animated illustration of elliptical orbits with different eccentricities. It also shows how the Sun is at the focus of an ellipse, and some of the math behind elliptical orbits. Beginner, intermediate and advanced versions of the content are available.

Roberta Johnson

2000-07-01

111

Constraining the Dust Coma Properties of Comet C/Siding Spring (2013 A1) at Large Heliocentric Distances  

E-print Network

The close encounter of Comet C/2013 A1 (Siding Spring) with Mars on October 19, 2014 presented an extremely rare opportunity to obtain the first flyby quality data of the nucleus and inner coma of a dynamically new comet. However, the comet's dust tail potentially posed an impact hazard to those spacecraft. To characterize the comet at large heliocentric distances, study its long-term evolution, and provide critical inputs to hazard modeling, we imaged C/Siding Spring with the Hubble Space Telescope when the comet was at 4.58, 3.77, and 3.28 AU from the Sun. The dust production rate, parameterized by the quantity Af$\\rho$, was 2500, 2100, and 1700 cm (5000-km radius aperture) for the three epochs, respectively. The color of the dust coma is 5.0$\\pm$0.3$\\%$/100 nm for the first two epochs, and 9.0$\\pm$0.3$\\%$/100 nm for the last epoch, and reddens with increasing cometocentric distance out to ~3000 km from the nucleus. The spatial distribution and the temporal evolution of the dust color are most consistent wi...

Li, Jian-Yang; Kelley, Michael S P; Farnham, Tony L; A'Hearn, Michael F; Mutchler, Max J; Lisse, Carey M; Delamere, W Alan

2014-01-01

112

The Hot Orbit: Orbital Cellulitis  

PubMed Central

Orbital cellulitis is an uncommon condition previously associated with severe complications. If untreated, orbital cellulitis can be potentially sight and life threatening. It can affect both adults and children but has a greater tendency to occur in the pediatric age group. The infection most commonly originates from sinuses, eyelids or face, retained foreign bodies, or distant soources by hematogenous spread. It is characterized by eyelid edema, erythema, chemosis, proptosis, blurred vision, fever, headache, and double vision. A history of upper respiratory tract infection prior to the onset is very common especially in children. In the era prior to antibiotics, vision loss from orbital cellulitis was a dreaded complication. Currently, imaging studies for detection of orbital abcess, the use of antibiotics and early drainage have mitigated visual morbidity significantly. The purpose of this review is to describe current investigative strategies and management options in the treatment of orbital cellulitis, establish their effectiveness and possible complications due to late intervention. PMID:22346113

Chaudhry, Imtiaz A.; Al-Rashed, Waleed; Arat, Yonca O.

2012-01-01

113

Long-term evaluation of three-dimensional heliocentric solar sail trajectories with arbitrary fixed sail setting  

Microsoft Academic Search

The solar radiation effects upon the orbital behaviour of an arbitrarily shaped spacecraft (or a solar sail in particular) in a general fixed orientation with respect to the local coordinate frame are investigated. Through introduction of a quasi-angle in the osculating plane, the motion of the orbital plane becomes uncoupled from the in-plane perturbations. Exact solutions in the form of

J. C. Van Der Ha; V. J. Modi

1979-01-01

114

Dynamical behaviour of planetesimals temporarily captured by a planet from heliocentric orbits: basic formulation and the case of low random velocity  

Microsoft Academic Search

Planetesimals encountering with a planet cannot be captured permanently unless energy dissipation is taken into account, but some of them can be temporarily captured in the vicinity of the planet for an extended period of time. Such a process would be important for the origin and dynamical evolution of irregular satellites, short-period comets, and Kuiper-belt binaries. In this paper, we

Kazunori Iwasaki; Keiji Ohtsuki

2007-01-01

115

Orbital Myiasis  

PubMed Central

Purpose To present a case of massive orbital myiasis. Case Report An 87-year-old debilitated woman suffering from left ocular pain of four days’ duration presented with a severely necrotized left orbit and several attached live larvae. The upper and lower eyelids and the eyeball were completely destroyed. She had history of eyelid surgery in the same eye due to a skin lesion, apparently some type of skin cancer, 15 years before. The larvae were identified as Chrysomya bezziana (Diptera: Calliphoridae) or old world screwworm fly. Conclusion Infestation of ocular and orbital tissues by fly larvae (ophthalmomyiasis) progresses rapidly and can completely destroy orbital tissues within days, especially in patients with poor general health. Treatment consists of removal of the larvae and surgical debridement. PMID:22454736

Khataminia, Gholamreza; Aghajanzadeh, Roja; Vazirianzadeh, Babak; Rahdar, Mahmoud

2011-01-01

116

UVCS\\/SOHO Observations of H I Lyman Alpha Line Profiles in Coronal Holes at Heliocentric Heights Above 3.0 R?  

Microsoft Academic Search

The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) has been used to measure\\u000a spectral line profiles for H I Ly? in the south polar coronal hole at projected heliocentric heights from 3.5 to 6.0 R? during 1998 January 5–11. Observations from 1.5 to 2.5 R? were made for comparison. The H I Ly? profile is the

R. M. Suleiman; J. L. Kohl; A. V. Panasyuk; A. Ciaravella; S. R. Cranmer; L. D. Gardner; R. Frazin; R. Hauck; P. L. Smith; G. Noci

1999-01-01

117

Latitude variation of recurrent MeV-energy proton flux enhancements in the heliocentric radial range 11 t 20 AU and possible correlation with solar coronal hole dynamics  

Microsoft Academic Search

Recurrent low energy (> or approx. =0.5 MeV) proton flux enhancements, reliable indicators of corotating plasma interaction regions in interplanetary space, have been observed on the Voyager 1 and 2 and Pioneer 11 spacecraft in the heliographic latitude range 2°S to 23°N and the heliocentric radial range 11 to 20 AU. After a period of rather high correlation between fluxes

S. P. Christon; E. C. Stone

1985-01-01

118

Analysis and interpretation of CCD data on P/Halley and physical parameters and activity status of cometary nuclei at large heliocentric distance  

NASA Technical Reports Server (NTRS)

The scientific objectives were as follows: (1) to construct a well sampled photometric time series of comet Halley extending to large heliocentric distances both post and pre-perihelion passage and derive a precise ephemeris for the nuclear spin so that the physical and chemical characteristics of individual regions of activity on the nucleus can be determined; and (2) to extend the techniques in the study of Comet Halley to the study of other cometary nuclei and to obtain new observational data.

Belton, Michael J. S.; Mueller, Beatrice

1991-01-01

119

A STUDY OF THE HELIOCENTRIC DEPENDENCE OF SHOCK STANDOFF DISTANCE AND GEOMETRY USING 2.5D MAGNETOHYDRODYNAMIC SIMULATIONS OF CORONAL MASS EJECTION DRIVEN SHOCKS  

SciTech Connect

We perform four numerical magnetohydrodynamic simulations in 2.5 dimensions (2.5D) of fast coronal mass ejections (CMEs) and their associated shock fronts between 10 Rs and 300 Rs. We investigate the relative change in the shock standoff distance, {Delta}, as a fraction of the CME radial half-width, D {sub OB} (i.e., {Delta}/D {sub OB}). Previous hydrodynamic studies have related the shock standoff distance for Earth's magnetosphere to the density compression ratio (DR; {rho} {sub u}/{rho} {sub d}) measured across the bow shock. The DR coefficient, k {sub dr}, which is the proportionality constant between the relative standoff distance ({Delta}/D {sub OB}) and the compression ratio, was semi-empirically estimated as 1.1. For CMEs, we show that this value varies linearly as a function of heliocentric distance and changes significantly for different radii of curvature of the CME's leading edge. We find that a value of 0.8 {+-} 0.1 is more appropriate for small heliocentric distances (<30 Rs) which corresponds to the spherical geometry of a magnetosphere presented by Seiff. As the CME propagates its cross section becomes more oblate and the k {sub dr} value increases linearly with heliocentric distance, such that k {sub dr} = 1.1 is most appropriate at a heliocentric distance of about 80 Rs. For terrestrial distances (215 Rs) we estimate k {sub dr} = 1.8 {+-} 0.3, which also indicates that the CME cross-sectional structure is generally more oblate than that of Earth's magnetosphere. These alterations to the proportionality coefficients may serve to improve investigations into the estimates of the magnetic field in the corona upstream of a CME as well as the aspect ratio of CMEs as measured in situ.

Savani, N. P. [University Corporation for Atmospheric Research (UCAR), Boulder, CO 80307 (United States); Shiota, D. [Computational Astrophysics Laboratory, Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kusano, K. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Vourlidas, A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Lugaz, N., E-mail: neel.savani02@imperial.ac.uk [Experimental Space Plasma Group, University of New Hampshire, Durham, NH 03824 (United States)

2012-11-10

120

Space-based Search for Transiting Exoplanets Orbiting Bright Stars  

NASA Astrophysics Data System (ADS)

At the current stage of research transiting planets hold the key to advancing our knowledge of exoplanets as they are the only targets that allow determination of many of the key plane-tary parameters. Because the employed techniques are differential (either photometry or spec-troscopy) and the planet is significantly fainter the host star the dominant limitation is simply the number of photons. This puts a very high premium on transiting planets with bright parent stars. The ExoPlanet Task Force recognized the high value of planets transiting bright stars and identified the need to perform a wide area space-based transit survey. In this presentation I will describe a program that addresses the ExoPTF recommendation by using the output of one of the instruments on the currently operating space mission STEREO. STEREO is the third mission in NASA's Solar Terrestrial Probes program. It uses two nearly identical spacecrafts -one on an Earth-leading orbit and one on an Earth-trailing orbit -each equipped with a suit of five small telescopes to provide a stereoscopic view of the coronal mass ejections (CME) as they propagate away from the Sun. As each of these telescopes observes a portion of the heliospehre, they also image the star field in the background. For the purposes of this study we will consider only the images obtained by the HI-1 instruments. Other instruments, although showing the stellar background as well, do not have the data output suitable for a search for transiting exoplanets. This project described here has the potential of delivering a number of very high value targets for follow-up studies with a wide range of facilities, both ground-based and space-based. It will provide a complete survey of all bright stars (<10m) for 18% of the sky. The photometric data series have the sensitivity to detect all transiting hot-Jupiters and other gas giants with periods up to ˜20 days and even some Neptune size planets orbiting bright and/or late type stars. On the extreme bright end, the survey is sensitive to some super-Earth size planets, but the available number of target stars is small. In my presentation I will describe the capabilities and limitations of the project, will demon-strate the utility of the HI-1 images for searching for transiting exoplanets, and will describe the existing data for several RV discovered planets.

Tsvetanov, Zlatan

121

Heliocentric evolution of the degradation of polyoxymethylene: Application to the origin of the formaldehyde (H 2CO) extended source in Comet C/1995 O1 (Hale-Bopp)  

NASA Astrophysics Data System (ADS)

The H 2CO production rates measured in Comet C/1995 O1 (Hale-Bopp) from radio wavelength observations [Biver, N., and 22 colleagues, 2002a. Earth Moon Planets 90, 5-14] showed a steep increase with decreasing heliocentric distance. We studied the heliocentric evolution of the degradation of polyoxymethylene (formaldehyde polymers: ( sbnd CH 2sbnd O sbnd ) n, also called POM) into gaseous H 2CO. POM decomposition can indeed explain the H 2CO density profile measured in situ by Giotto spacecraft in the coma of Comet 1P/Halley, which is not compatible with direct release from the nucleus [Cottin, H., Bénilan, Y., Gazeau, M.-C., Raulin, F., 2004. Icarus 167, 397-416]. We show that the H 2CO production curve measured in Comet C/1995 O1 (Hale-Bopp) can be accurately reproduced by this mechanism with a few percents by mass of solid POM in grains. The steep heliocentric evolution is explained by the thermal degradation of POM at distances less than 3.5 AU. This study demonstrates that refractory organics present in cometary dust can significantly contribute to the composition of the gaseous coma. POM, or POM-like polymers, might be present in cometary grains. Other molecules, like CO and HNC, might also be produced by a similar process.

Fray, Nicolas; Bénilan, Yves; Biver, Nicolas; Bockelée-Morvan, Dominique; Cottin, Hervé; Crovisier, Jacques; Gazeau, Marie-Claire

2006-09-01

122

A simple procedure to extend the Gauss method of determining orbital parameters from three to N points  

NASA Astrophysics Data System (ADS)

A simple procedure is developed to determine orbital elements of an object orbiting in a central force field which contribute more than three independent celestial positions. By manipulation of formal three point Gauss method of orbit determination, an initial set of heliocentric state vectors r i and is calculated. Then using the fact that the object follows the path that keep the constants of motion unchanged, I derive conserved quantities by applying simple linear regression method on state vectors r i and . The best orbital plane is fixed by applying an iterative procedure which minimize the variation in magnitude of angular momentum of the orbit. Same procedure is used to fix shape and orientation of the orbit in the plane by minimizing variation in total energy and Laplace Runge Lenz vector. The method is tested using simulated data for a hypothetical planet rotating around the sun.

Mirtorabi, Taghi

2014-01-01

123

Nuclear reactor power for an electrically powered orbital transfer vehicle  

NASA Technical Reports Server (NTRS)

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low earth orbit (LEO) and geosynchronous earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant.

Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Fujita, T.; Grossman, M.; Kia, T.; Nesmith, B.

1987-01-01

124

Nuclear reactor power for an electrically powered orbital transfer vehicle  

SciTech Connect

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low earth orbit (LEO) and geosynchronous earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant.

Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Fujita, T.; Grossman, M.; Kia, T.; Nesmith, B.

1987-05-01

125

Orbit Determination Accuracy for Comets on Earth-Impacting Trajectories  

NASA Technical Reports Server (NTRS)

The results presented show the level of orbit determination accuracy obtainable for long-period comets discovered approximately one year before collision with Earth. Preliminary orbits are determined from simulated observations using Gauss' method. Additional measurements are incorporated to improve the solution through the use of a Kalman filter, and include non-gravitational perturbations due to outgassing. Comparisons between observatories in several different circular heliocentric orbits show that observatories in orbits with radii less than 1 AU result in increased orbit determination accuracy for short tracking durations due to increased parallax per unit time. However, an observatory at 1 AU will perform similarly if the tracking duration is increased, and accuracy is significantly improved if additional observatories are positioned at the Sun-Earth Lagrange points L3, L4, or L5. A single observatory at 1 AU capable of both optical and range measurements yields the highest orbit determination accuracy in the shortest amount of time when compared to other systems of observatories.

Kay-Bunnell, Linda

2004-01-01

126

Nuclear reactor power for an electrically powered orbital transfer vehicle  

SciTech Connect

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low Earth orbit (LEO) and geosynchronous Earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to Earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant.

Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Fujita, T.; Grossman, M.; Kia, T.; Nesmith, B.

1987-01-01

127

Orbital Debris  

NASA Technical Reports Server (NTRS)

Earth orbital debris issues and recommended future activities are discussed. The workshop addressed the areas of environment definition, hazards to spacecraft, and space object management. It concluded that orbital debris is a potential problem for future space operations. However, before recommending any major efforts to control the environment, more data are required. The most significant required data are on the population of debris smaller than 4 cm in diameter. New damage criteria are also required. When these data are obtained, they can be combined with hypervelocity data to evaluate the hazards to future spacecraft. After these hazards are understood, then techniques to control the environment can be evaluated.

Kessler, D. J. (compiler); Su, S. Y. (compiler)

1985-01-01

128

Elliptical Orbits  

NSDL National Science Digital Library

Although not inquiry, this activity is important for students to understand what an ellipse is and what a focus is, and to break misconceptions about Earth's orbit being highly elliptical. This is the perfect place to check to see if students have the mis

Michael Horton

2009-05-30

129

Orbital Surgery  

MedlinePLUS

The orbit is the boney socket in your skull that contains and houses the eye and all the associated structures that support the function of the eye ... variety of problems can occur in the eye socket that effect the function of the eye. These ...

130

Orbital Elements  

NSDL National Science Digital Library

Coordinates for tracking the International Space Station and the Mir Space Station are available here from NASA's Johnson Space Center Flight Design and Dynamics Division. The Orbital Elements page offers real-time data for use in ground track plotting programs. The site cautions the data are for ground track plotting programs only and "should not be used for precise applications or analysis!"

131

Pupils Produce their Own Narratives Inspired by the History of Science: Animation Movies Concerning the Geocentric-Heliocentric Debate  

NASA Astrophysics Data System (ADS)

In this paper, we present the design and application of a teaching scenario appropriate for 12-years-old pupils in the primary school aiming to a better understanding of scientific concepts and scientific methods, linking the development of individual thinking with the development of scientific ideas and facilitating a better understanding of the nature of science. The design of the instructional material supporting this scenario has been based on the study of the history of astronomy and especially on: (a) The various theories concerning the movement of Earth, our solar system and the universe. (b) Key-stories highlighting the evolutionary character of scientific knowledge as well as the cultural interrelations of science and society. The design of the teaching scenario has focused on the participation of pupils in gradually evolving discourses and practices encouraging an appreciation of aspects of the nature of science (e.g. the role of observation and hypothesis, the use of evidence, the creation and modification of models). In this case, pupils are asked to produce their own narratives: animation movies concerning the geocentric-heliocentric debate inspired by the history of science, as the animation technique presents strong expressional potential and currently has many applications in the field of educational multimedia. The research design of this current case study has been based on the SHINE research model, while data coming from pupils' animation movies, questionnaires, interviews, worksheets, story-boards and drawings have been studied and analyzed using the GNOSIS research model. Elaborated data coming from our analysis approach reveal the appearance, transformation and evolution of aspects of nature of science appreciated by pupils and presented in their movies. Data analysis shows that during the application pupils gradually consider more and more the existence of multiple answers in scientific questions, appreciate the effect of culture on the way science functions and the way scientists work as well as the effect of new scientific interpretations that replace the old ones in the light of new evidence. The development of pupils' animation movies carrying aspects of the history of astronomy with a strong focus on the understanding of the nature of science creates a dynamic educational environment that facilitates pupils' introduction to a demanding teaching content (e.g. planet, model, retrograde motion) placing it in context (key-stories from the history of science) and at the same time offers to pupils the opportunity to engage their personal habits, interests and hobbies in the development of their science movies.

Piliouras, Panagiotis; Siakas, Spyros; Seroglou, Fanny

2011-07-01

132

Orbital Evolution of Impact Ejecta from Ganymede  

NASA Astrophysics Data System (ADS)

We have numerically computed the orbital evolution of ˜10 3 particles representing high-speed ejecta from Gilgamesh, the largest impact basin on Ganymede. The integration includes the four Galilean satellites, Jupiter (including J2 and J4), Saturn, and the Sun. The integrations last 100,000 years. The particles are ejected at a variety of speeds and directions, with the fastest particles ejected at 1.4 times the escape speed vesc? 2GM G/R G of Ganymede. Ejecta with speeds v<0.96 vesc follow suborbital trajectories. At v˜0.96 vesc there is a transition characterized by complex behavior suggestive of chaos. For v>0.96 vesc, most particles escape Ganymede and achieve orbits about Jupiter. Eventually most (˜71%) of the jovicentric particles hit Ganymede, with 92% of these hitting within 1000 years. The accretion rate scales as 1/ t. Their impact sites are randomly distributed, as expected for planetocentric debris. We estimate that most of the resulting impact craters are a few kilometers across and smaller. The rest of the escaping ejecta are partitioned as follows: ˜3% hit Io; ˜10% hit Europa; ˜13% hit Callisto; 2% reach heliocentric space; and less than ˜1% hit Jupiter. Only two particles survived the entire 10 5-year integration. Ejecta from large impact events do not appear to be a plausible source of large craters on the Galilean satellites; however, such ejecta may account for the majority of small craters.

Alvarellos, Jose Luis; Zahnle, Kevin J.; Dobrovolskis, Anthony R.; Hamill, Patrick

2002-11-01

133

Orbital Effects on Mercury's Escaping Sodium Exosphere  

NASA Technical Reports Server (NTRS)

We present results from coronagraphic imaging of Mercury's sodium tail over a 7 deg field of view. Several sets of observations made at the McDonald Observatory since May 2007 show a tail of neutral sodium atoms stretching more than 1000 Mercury radii (R(sub m)) in length, or a full degree of sky. However, no tail was observed extending beyond 120 R(sub m) during the January 2008 MESSENGER Fly-by period, or during a similar orbital phase of Mercury in July 2008. Large changes in Mercury's heliocentric radial velocity cause Doppler shifts about the Fraunhofer absorption features; the resultant change in solar flux and radiation pressure is the primary cause of the observed variation in tail brightness. Smaller fluctuations in brightness may exist due to changing source rates at the surface, but we have no explicit evidence for such changes in this data set. The effects of radiation pressure on Mercury's escaping atmosphere are investigated using seven observations spanning different orbital phases. Total escape rates of atmospheric sodium are estimated to be between 5 and 13 x 10(exp 23) atoms/s and show a correlation to radiation pressure. Candidate sources of Mercury's sodium exosphere include desorption by UV sunlight, thermal desorption, solar wind channeled along Mercury's magnetic field lines, and micro-meteor impacts. Wide-angle observations of the full extent of Mercury's sodium tail offer opportunities to enhance our understanding of the time histories of these source rates.

Schmidt, Carl A.; Wilson, Jody K.; Baumgardner, Jeffrey; Mendillo, Michael

2009-01-01

134

Eye and orbit ultrasound  

MedlinePLUS

Echography - eye orbit; Ultrasound - eye orbit; Ocular ultrasonography; Orbital ultrasonography ... eye is numbed with medicine (anesthetic drops). The ultrasound wand (transducer) is placed against the front surface ...

135

Orbiting Hotel  

NSDL National Science Digital Library

It is the year 2025 and a large company, Z-Tech, wants to put a hotel in space having it orbit around one of the planets in our solar system. Our 9th grade class has been given a very important job. We have to search for the perfect location for the hotel. Our job is to report back to the company with the planet that is the best place for an orbiting hotel. The Task: You are to write a report recommending which planet should be chosen. Your report should include pictures of the planet you recommended. Here are the questions you should answer in order to report back to Z-Tech with your recommendation. * Which planet will be the ...

Mrs. Hicken

2009-10-19

136

Achieving Orbit  

NSDL National Science Digital Library

In this Engineering Design Challenge activity, participants use balloons to investigate how a two-stage rocket, like that used in the IBEX mission, can propel a satellite to a specific orbit. Participants will construct a two-stage balloon that will be required to reach a particular location on the balloon track, simulating the proper orbit to be reached by the IBEX satellite. This activity is adapted from the NASA Rockets Educators Guide (EG-2003-01-108-HQ) and the NASA Glenn Research Center’s online Learning Technologies Project for facilitation with an informal museum audience. Each short activity/product helps to build awareness and engagement in the science and engineering aspects of the mission that is reinforced as visitors choose to participate in more activities, including viewing the planetarium show and mission Web site.

Michelle Nichols

2008-01-15

137

Data catalog series for space science and applications flight missions. Volume 1B: Descriptions of data sets from planetary and heliocentric spacecraft and investigations  

NASA Technical Reports Server (NTRS)

The main purpose of the data catalog series is to provide descriptive references to data generated by space science flight missions. The data sets described include all of the actual holdings of the Space Science Data Center (NSSDC), all data sets for which direct contact information is available, and some data collections held and serviced by foreign investigators, NASA and other U.S. government agencies. This volume contains narrative descriptions of planetary and heliocentric spacecraft and associated experiments. The following spacecraft series are included: Mariner, Pioneer, Pioneer Venus, Venera, Viking, Voyager, and Helios. Separate indexes to the planetary and interplanetary missions are also provided.

Horowitz, Richard (compiler); Jackson, John E. (compiler); Cameron, Winifred S. (compiler)

1987-01-01

138

Data catalog series for space science and applications flight missions. Volume 1A: Descriptions of planetary and heliocentric spacecraft and investigations, second edition  

NASA Technical Reports Server (NTRS)

The main purpose of the data catalog series is to provide descriptive references to data generated by space science flight missions. The data sets described include all of the actual holdings of the Space Science Data Center (NSSDC), all data sets for which direct contact information is available, and some data collections held and serviced by foreign investigators, NASA and other U.S. government agencies. This volume contains narrative descriptions of planetary and heliocentric spacecraft and associated experiments. The following spacecraft series are included: Mariner, Pioneer, Pioneer Venus, Venera, Viking, Voyager, and Helios. Separate indexes to the planetary and interplanetary missions are also included.

Cameron, Winifred Sawtell (editor); Vostreys, Robert W. (editor)

1988-01-01

139

Orbital Evolution of Extra-Solar Giant Planets  

NASA Astrophysics Data System (ADS)

The recent discoveries (Mayor and Queloz, 1995; Marcy and Butler, 1996; Butler and Marcy, 1996) of extra-solar giant planets (EGPs) at small heliocentric distances have prompted questions about the formation, evolution, and migration of these EGPs. The location of several EGPs at much less than 1 AU from their primaries has proved to be particularly problematic. Since it is thought that EGPs do not form that close to their primaries (Guillot et al., 1996), a reasonable conclusion is that these close companions formed elsewhere in their solar systems and subsequently moved to their present small heliocentric distances. Jupiter-style planetary formation is thought to initiate at the ice line ( ~ several AU) (Boss, 1995), with possible subsequent inward migration (Lin and Papaloizou, 1986). But how can a massive body stop its inward migration before crashing into its star? We investigate the orbital evolution of an EGP with our fully implicit numerical model. Inward migration is caused by angular momentum exchange between the planet and disk (Takeuchi et al., 1996, Lin and Papaloizou, 1986). After the planet has migrated to much less than 1 AU, its inward motion can be halted by outward torques due to tides (Lin et al., 1996) and due to angular momentum exchange from Roche lobe overflow and mass loss (Benz et al., 1990). EGPs may stably survive, some at new, smaller masses, at small heliocentric distances for greater than 10(7) years, by which time the disk has dissipated (Zuckerman et al., 1995) and the torques have nearly vanished. This mechanism may explain the presence of EGPs at small heliocentric distances. References: Benz et al., 1990, Ap. J., 348, 647. Boss, 1995, Science, 267, 360. Butler and Marcy, 1996, Ap. J., 464, L153. Guillot et al., 1996, Ap. J., 459, L35. Lin et al., 1996, Nature, 380, 606. Lin and Papaloizou, 1986, Ap. J., 309, 846. Marcy and Butler, 1996, Ap. J., 464, L147. Mayor and Queloz, 1995, Nature, 378, 355. Takeuchi et al., 1996, Ap. J., 460, 832. Zuckerman et al., 1995, Nature, 373, 494. Acknowledgement: This work is supported in part under an NSF Graduate Research Fellowship.

Trilling, D. E.; Benz, W.; Guillot, T.; Lunine, J. I.

1996-09-01

140

Inflammation of the Orbit  

MedlinePLUS

... Socket Disorders 4 Inflammation of the Orbit (Inflammatory Orbital Pseudotumor) Any or all of the structures within the ... entire orbit and its contents is called inflammatory orbital pseudotumor (which is not really a tumor and is ...

141

Orbit analysis  

SciTech Connect

The past fifteen years have witnessed a remarkable development of methods for analyzing single particle orbit dynamics in accelerators. Unlike their more classic counterparts, which act upon differential equations, these methods proceed by manipulating Poincare maps directly. This attribute makes them well matched for studying accelerators whose physics is most naturally modelled in terms of maps, an observation that has been championed most vigorously by Forest. In the following sections the author sketchs a little background, explains some of the physics underlying these techniques, and discusses the best computing strategy for implementing them in conjunction with modeling accelerators.

Michelotti, L.

1995-01-01

142

Multiple Solutions in Preliminary Orbit Determination from Three Observations  

E-print Network

.2), relating the geocentric distance of the body to its heliocentric distance at a fixed time (see) for the heliocentric distance of the celestial body. Actually more than one solution of (A.4) may exist, and this can and i the declination of the body at time ti. Let qi be the heliocentric position vectors

Milani, Andrea

143

Everything in OrbitEverything in Orbit Orbital VelocityOrbital Velocity  

E-print Network

is the speed at which a planetary body moves in Orbital velocity is the speed at which a planetary body moves Escape velocity = "speed required to project a body completely Escape velocity = "speed requiredEverything in OrbitEverything in Orbit #12;Orbital VelocityOrbital Velocity Orbital velocity

Herrick, Robert R.

144

Rock-Around Orbits  

E-print Network

; !). Using these parameters, one can create an orbit that will surround the target orbit allowing the satellite in the Rock-Around Orbit (RAO) orbit to have a 360 degree view of RSOs in the target orbit. The RAO orbit can be applied to any circular...

Bourgeois, Scott K.

2010-07-14

145

Shapes of d Orbitals  

NSDL National Science Digital Library

Shapes of d Orbitals shows the d orbitals in an axis set. Running the mouse over an orbital reveals the "name" of that orbital. This is good practice for helping students link the name of an orbital to the orientation.Shapes of d Orbitals has a link to D Orbitals in an Octahedral Ligand Field. Here the user may click on the name of any one of the d orbitals to obtain a larger 3-dimensional image. The images are rotatable and scalable. Orbital phase is shown by the different colors.

146

Orbit design concepts for Jupiter orbiter missions  

NASA Technical Reports Server (NTRS)

Advanced mission and orbit planning efforts are currently in progress for a Mariner-class Jupiter orbiter. Baseline spacecraft and orbit design criteria are the goals of a NASA effort to define such a mission. Orbit design concepts that have been discovered during the early stages of mission planning are both challenging and exciting. A description is given of several such concepts that may greatly increase the flexibility and scientific return of orbiters designed for close study of the Galilean satellites and exploration of the Jovian system. Some new jargon is introduced in discussions to describe the exploitation of gravity-assist trajectories using the giant satellites for orbit control. Orbit 'pumping' and 'cranking' and 'resonance hopping' are defined and shown to be dynamically feasible means of controlling the orbit and, thus, the scientific return. A candidate encounter sequence is presented for an equatorial tour of the Galilean moons.

Uphoff, C.; Roberts, P. H.; Friedman, L. D.

1974-01-01

147

PROTOTYPING LHC ORBIT CONTROL  

Microsoft Academic Search

Orbit correction consists in varying the strengths of the corrector magnets to make the measured beam position match a predefined reference. In the two LHC rings, this involves around 1000 beam position monitors and over 500 orbit correctors in each plane. The orbit control loop of the LHC must be able to compensate orbit drifts at frequencies between 10?2 and

J. Wenninger; T. Wijnands; B. Srinivasan

2002-01-01

148

Orbital dystopia due to orbital roof defect.  

PubMed

We performed a retrospective review of patients who presented with delayed dystopia as a consequence of an orbital roof defect due to fractures and nontraumatic causes to search for a correlation between orbital roof defect size and surgical indications for the treatment thereof. Retrospective analyses were performed in 7 patients, all of whom presented with delayed dystopia due to orbital roof defects, between January 2001 and June 2011. The causes of orbital roof defects were displaced orbital roof fractures (5 cases), tumor (1 case), and congenital sphenoid dysplasia (1 case). All 7 patients had initially been treated conservatively and later presented with significant dystopia. The sizes of the defects were calculated on computed tomographic scans. Among the 7 patients, aspiration of cerebrospinal fluid, which caused ocular symptoms, in 1 patient with minimal displaced orbital roof and reconstruction with calvarial bone, titanium micromesh, or Medpor in 6 other patients were performed. The minimal size of the orbital roof in patients who underwent orbital roof reconstruction was 1.2 cm (defect height) x 1.0 cm (defect length), 0.94 cm(2). For all patients with orbital dystopia, displacement of the globe was corrected without any complications, regardless of whether the patient was evaluated grossly or by radiology. In this retrospective study, continuous monitoring of clinical signs and active surgical management should be considered for cases in which an orbital roof defect is detected, even if no definite symptoms are noted, to prevent delayed sequelae. PMID:24163861

Rha, Eun Young; Joo, Hong Sil; Byeon, Jun Hee

2013-01-01

149

Working With Orbits  

NSDL National Science Digital Library

This site offers two programs to illustrate how orbits work. The Orbital Elements calculator contains animations to see how the appearance of an orbit depends on the values of the orbital elements which include distance from the Sun, eccentricity, pericenter location and anomaly. This is available in two or three dimensions. The Solar System allows users to watch several planets in our Solar System simultaneously orbit the Sun. An additional object (asteroid or comet) is present and users change the orbital parameters to see what types of orbits are possible for this object.

Douglas Hamilton

150

Contingency Trajectory Design for a Lunar Orbit Insertion Maneuver Failure by the LADEE Spacecraft  

NASA Technical Reports Server (NTRS)

This paper presents results from a contingency trajectory analysis performed for the Lunar Atmosphere & Dust Environment Explorer (LADEE) mission in the event of a missed lunar-orbit insertion (LOI) maneuver by the LADEE spacecraft. The effects of varying solar perturbations in the vicinity of the weak stability boundary (WSB) in the Sun-Earth system on the trajectory design are analyzed and discussed. It is shown that geocentric recovery trajectory options existed for the LADEE spacecraft, depending on the spacecraft's recovery time to perform an Earth escape-prevention maneuver after the hypothetical LOI maneuver failure and subsequent path traveled through the Sun-Earth WSB. If Earth-escape occurred, a heliocentric recovery option existed, but with reduced science capacapability for the spacecraft in an eccentric, not circular near-equatorial retrograde lunar orbit.

Genova, A. L.

2014-01-01

151

Orbital fractures: a review  

PubMed Central

This review of orbital fractures has three goals: 1) to understand the clinically relevant orbital anatomy with regard to periorbital trauma and orbital fractures, 2) to explain how to assess and examine a patient after periorbital trauma, and 3) to understand the medical and surgical management of orbital fractures. The article aims to summarize the evaluation and management of commonly encountered orbital fractures from the ophthalmologic perspective and to provide an overview for all practicing ophthalmologists and ophthalmologists in training. PMID:21339801

Joseph, Jeffrey M; Glavas, Ioannis P

2011-01-01

152

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

Results from operational OD produced by the NASA Goddard Flight Dynamics Facility for the LRO nominal and extended mission are presented. During the LRO nominal mission, when LRO flew in a low circular orbit, orbit determination requirements were met nearly 100% of the time. When the extended mission began, LRO returned to a more elliptical frozen orbit where gravity and other modeling errors caused numerous violations of mission accuracy requirements. Prediction accuracy is particularly challenged during periods when LRO is in full-Sun. A series of improvements to LRO orbit determination are presented, including implementation of new lunar gravity models, improved spacecraft solar radiation pressure modeling using a dynamic multi-plate area model, a shorter orbit determination arc length, and a constrained plane method for estimation. The analysis presented in this paper shows that updated lunar gravity models improved accuracy in the frozen orbit, and a multiplate dynamic area model improves prediction accuracy during full-Sun orbit periods. Implementation of a 36-hour tracking data arc and plane constraints during edge-on orbit geometry also provide benefits. A comparison of the operational solutions to precision orbit determination solutions shows agreement on a 100- to 250-meter level in definitive accuracy.

Slojkowski, Steven E.

2014-01-01

153

Interactive Molecular Orbitals  

NSDL National Science Digital Library

The majority of Introductory Chemistry texts provide students with an adequate introduction to the visual aspects of the molecular orbital model for homonuclear diatomic molecules. The treatment of heteronuclear diatomic and polyatomic molecules is less uniform. Heteronuclear diatomics, when mentioned, are invariably treated as being derived from homonuclear diatomics. While the atomic orbital energy level differences in heteronuclear diatomics is sometimes pictured, the consequences of those differences for the resultant molecular orbitals are rarely discussed. The discussion of polyatomic molecular orbitals in these texts is limited to showing that parallel p-orbitals produce delocalized pi molecular orbitals. The molecules typically mentioned in this context are benzene, nitrate ion and carbonate ion. However, It is rarely pointed out that the six p-orbitals in benzene would form 6 pi molecular orbitals, and that only one of these orbitals would look like the picture in the text.These interactive modules are designed to clarify this subject.

154

A study of halo orbits at the Sun-Mars L1 Lagrangian point in the photogravitational restricted three-body problem  

NASA Astrophysics Data System (ADS)

Photogravitational Restricted Three-Body Problem (PGRTBP) is considered and halo orbits are generated in the vicinity of the Sun-Mars L1 Lagrangian point. Deviation of properties such as time period, size and velocity variation in the halo orbits with Sun as a source of radiation are discussed. With increase in solar radiation pressure, the halo orbits are found to elongate and move towards the Sun and the time period of the halo orbits is found to increase. The variation in the behaviour of invariant manifolds with change in radiation pressure is also computed and it is found that as the radiation pressure increases, the transition from Mars-centric path to heliocentric path is delayed. Certain implications of the velocity profile of the invariant manifolds are also discussed.

Eapen, Roshan Thomas; Sharma, Ram Krishan

2014-08-01

155

W-reps, nilp orbits, orbit method  

E-print Network

W reps nilp orbits W reps Explaining the arrows Remembrance of things past Weyl group Institute of Technology Lie groups: structure, actions and representations In honor of Joe Wolf, on his 75th of things past Outline What is representation theory about? Nilpotent orbits from G reps W reps from G reps

Vogan, David

156

Efficient orbit integration by orbital longitude methods  

NASA Astrophysics Data System (ADS)

Recently we developed a new formulation of numerical integration of orbital motion named manifold correction methods. The main trick is to keep rigorously the consistency of some physical relations such as that of the orbital energy, of the orbital angular momentum, or of the Laplace integral of a binary subsystem. This maintenance is done by applying a sort of correction to the integrated variables at every integration step. Typical methods of correction are certain geometric transformation such as the spatial scaling and the spatial rotation, which are commonly used in the comparison of reference frames, or mathematically-reasonable operations such as the modularization of angle variables into the standard domain [-?, ?). The finally-evolved form of the manifold correction methods is the orbital longitude methods, which enable us to conduct an extremely precise integration of orbital motions. In the unperturbed orbits, the integration errors are suppressed at the machine epsilon level for an infinitely long period. In the perturbed cases, on the other hand, the errors initially grow in proportion to the square root of time and then increase more rapidly, the onset time of which depends on the type and the magnitude of perturbations. This feature is also realized for highly eccentric orbits by applying the same idea to the KS-regularization. Expecially the introduction of time element greatly enhances the performance of numerical integration of KS-regularized orbits whether the scaling is applied or not.

Fukushima, Toshio

157

Atomic Orbital Shapes  

NSDL National Science Digital Library

This applet shows 3-dimensional representations of hydrogenic orbital surfaces. Orbital phase is shown by the different colors. The images are rotatable and scalable. This applet will run very slowly on older, slower machines.

158

Lunar orbiting prospector  

NASA Technical Reports Server (NTRS)

One of the prime reasons for establishing a manned lunar presence is the possibility of using the potential lunar resources. The Lunar Orbital Prospector (LOP) is a lunar orbiting platform whose mission is to prospect and explore the Moon from orbit in support of early lunar colonization and exploitation efforts. The LOP mission is divided into three primary phases: transport from Earth to low lunar orbit (LLO), operation in lunar orbit, and platform servicing in lunar orbit. The platform alters its orbit to obtain the desired surface viewing, and the orbit can be changed periodically as needed. After completion of the inital remote sensing mission, more ambitious and/or complicated prospecting and exploration missions can be contemplated. A refueled propulsion module, updated instruments, or additional remote sensing packages can be flown up from the lunar base to the platform.

1988-01-01

159

THE RHIC ORBIT CONTROL  

Microsoft Academic Search

The paper describes the methods used at RHIC collider for both global orbit correction over the whole ring and lo- cal orbit control in particular regions. Most routinely used tools of the local orbit control include the beam separa- tion, to avoid beam-beam effects at the acceleration, and the beam steering for collisions. The correction on the ramp uses feed-forward

V. Ptitsyn; T. Satogata

160

Mars Reconnaissance Orbiter  

NSDL National Science Digital Library

This is the mission web site for the Mars Reconnaissance Orbiter, which went into orbit around Mars on March 10, 2006. The site provides links to updates and information about the project. The site features links to Mars Reconnaissance Orbiter images, animations, and datasets. Science operations commence in November, 2006.

Jet Propulsion Laboratory

161

Five Equivalent d Orbitals  

ERIC Educational Resources Information Center

Amplifies and clarifies a previous paper on pyramidal d orbitals. Discusses two sets of pyramid d orbitals with respect to their maximum bond strength and their symmetry. Authors described the oblate and prolate pentagonal antiprisms arising from the two sets of five equivalent d orbitals. (RR)

Pauling, Linus; McClure, Vance

1970-01-01

162

Orbital-Lifetime Program  

NASA Technical Reports Server (NTRS)

Orbital Lifetime Program (OL) analyzes long-term motion of Earthorbiting spacecraft at altitudes of up to 2,500 km. Models perturbations to orbit caused by solar-radiation pressure, atmospheric drag, and gravitational effects of Sun, Moon, and oblate Earth. Used to predict orbital lifetime and decay rate of satellites. OL written in FORTRAN 77.

Orr, L. H.

1986-01-01

163

SEASAT B orbit synthesis  

NASA Technical Reports Server (NTRS)

Addition were made to Battelle's Interactive Graphics Orbit Selection (IGOS) program; IGOS was exercised via telephone lines from JPL, and candidate SEASAT orbits were analyzed by Battelle. The additions to the program enable clear understanding of the implications of a specific orbit to the diverse desires of the SEASAT user community.

Rea, F. G.; Warmke, J. M.

1976-01-01

164

Reflection Model as Applied for the Analysis of Enhancements of Solar Cosmic Rays at Different Heliocentric Distances: An Example of the Event Observed in June 1991 onboard GRANAT and ULYSSES Spacecraft  

Microsoft Academic Search

In this paper we consider a large-scale enhancement of the intensity of solar protons (E = 1–20 MeV) observed in June 1991 for 26 days at different points of interplanetary space, onboard ULYSSES (in the time period under consideration it was located at a heliocentric distance of 3 AU, at an angular distance of ~70° to the East of the

E. E. Grigorenko; G. P. Lyubimov

2004-01-01

165

Orbit Software Suite  

NASA Technical Reports Server (NTRS)

Orbit Software Suite is used to support a variety of NASA/DM (Dependable Multiprocessor) mission planning and analysis activities on the IPS (Intrusion Prevention System) platform. The suite of Orbit software tools (Orbit Design and Orbit Dynamics) resides on IPS/Linux workstations, and is used to perform mission design and analysis tasks corresponding to trajectory/ launch window, rendezvous, and proximity operations flight segments. A list of tools in Orbit Software Suite represents tool versions established during/after the Equipment Rehost-3 Project.

Osgood, Cathy; Williams, Kevin; Gentry, Philip; Brownfield, Dana; Hallstrom, John; Stuit, Tim

2012-01-01

166

OTV orbital tanking systems  

NASA Technical Reports Server (NTRS)

Orbital transfer of cryogenic propellants could benefit spacecraft and Orbital Transfer Vehicle (OTV) missions in the 1980s by supplying main propulsion, attitude control, or other fluid systems. The Space Shuttle can operate as a tanker when equipped with cryogenic propellant storage and orbital transfer systems. The key technologies are multilayer insulation, capillary propellant acquisition, zero-g gaging, orbital chilldown, and possibly large flight weight dewars. The technologies and operations could be realistically demonstrated using a Centaur that has been integrated with the Shuttle. Orbital refueling capability can enhance the usefulness of the whole Shuttle program

Heald, D. A.; Merino, F.

1979-01-01

167

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

LRO definitive and predictive accuracy requirements were easily met in the nominal mission orbit, using the LP150Q lunar gravity model. center dot Accuracy of the LP150Q model is poorer in the extended mission elliptical orbit. center dot Later lunar gravity models, in particular GSFC-GRAIL-270, improve OD accuracy in the extended mission. center dot Implementation of a constrained plane when the orbit is within 45 degrees of the Earth-Moon line improves cross-track accuracy. center dot Prediction accuracy is still challenged during full-Sun periods due to coarse spacecraft area modeling - Implementation of a multi-plate area model with definitive attitude input can eliminate prediction violations. - The FDF is evaluating using analytic and predicted attitude modeling to improve full-Sun prediction accuracy. center dot Comparison of FDF ephemeris file to high-precision ephemeris files provides gross confirmation that overlap compares properly assess orbit accuracy.

Slojkowski, Steven E.

2014-01-01

168

Painless orbital myositis.  

PubMed

Idiopathic orbital inflammation is the third most common orbital disease, following Graves orbitopathy and lymphoproliferative diseases. We present a 11 year old girl with 15 days history of painless diplopia. There was no history of fluctuation of symptoms, drooping of eye lids or diminished vision. She had near total restricted extra-ocular movements and mild proptosis of the right eye. There was no conjunctival injection, chemosis, or bulb pain. There was no eyelid retraction or lid lag. Rest of the neurological examination was unremarkable.Erythrocyte sedimentation rate was raised with eosinophilia. Antinuclear antibodies were positive. Liver, renal and thyroid functions were normal. Antithyroid, double stranded deoxyribonucleic acid and acetylcholine receptor antibodies were negative. Repetitive nerve stimulation was negative. Magnetic resonance imaging (MRI) of the orbit was typical of orbital myositis. The patient responded to oral steroids. Orbital myositis can present as painless diplopia. MRI of orbit is diagnostic in orbital myositis. PMID:22919201

Chakor, Rahul T; Santhosh, N S

2012-07-01

169

Controlling the NGST Orbit  

NASA Astrophysics Data System (ADS)

NGST will likely be placed in an elliptical orbit around the external collinear Lagrange point L2. However, the orbit is dynamically unstable and on-board thrusters must be used to make corrections to the orbit over time. The limited fuel available for such corrections may well limit the mission lifetime. Due to its large (200 m2) heat shield, NGST will be subject to significant perturbations by solar radiation pressure. We present an analysis for controlling the orbit against various perturbations, including solar radiation pressure. Ignoring effects of nonlinearity, we obtain an analytic description of the orbital evolution subject to arbitrary time-dependent perturbations. Orbital instability can be controlled by minimizing the effects of secular growing terms. Several control strategies are described. These strategies include the optimal use of thrusters and the selection of an appropriate orbit which compensates for perturbations.

Lubow, S. H.

2001-11-01

170

Efficient orbit integration by orbital longitude methods  

NASA Astrophysics Data System (ADS)

Triggered by the desire to investigate numerically the planetary precession through a long-term numerical integration of the solar system, we developed a new formulation of numerical integration of orbital motion named manifold correction methods. The main trick is to keep rigorously the consistency of some physical relations such as that of the orbital energy, of the orbital angular momentum, or of the Laplace integral of a binary subsystem. This maintenance is done by applying a sort of correction to the integrated variables at every integration step. Typical methods of correction are certain geometric transformation such as the spatial scaling and the spatial rotation, which are commonly used in the comparison of reference frames, or mathematically-reasonable operations such as the modularization of angle variables into the standard domain [-?,?). The finally-evolved form of the manifold correction methods is the orbital longitude methods, which enable us to conduct an extremely precise integration of orbital motions. In the unperturbed orbits, the integration errors are suppressed at the machine epsilon level for an infinitely long period. In the perturbed cases, on the other hand, the errors initially grow in proportion to the square root of time and then increase more rapidly, the onset time of which depends on the type and the magnitude of perturbations. This feature is also realized for highly eccentric orbits by applying the same idea to the KS-regularization. Especially the introduction of time element greatly enhances the performance of numerical integration of KS-regularized orbits whether the scaling is applied or not.

Fukushima, T.

2005-09-01

171

What do the orbital motions of the outer planets of the Solar System tell us about the Pioneer anomaly?  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the effects that an anomalous acceleration as that experienced by the Pioneer spacecraft after they passed the 20 AU threshold would induce on the orbital motions of the Solar System planets placed at heliocentric distances of 20 AU or larger as Uranus, Neptune and Pluto. It turns out that such an acceleration, with a magnitude of 8.74 × 10 -10 m s -2, would affect their orbits with secular and short-period signals large enough to be detected according to the latest published results by E.V. Pitjeva, even by considering errors up to 30 times larger than those released. The absence of such anomalous signatures in the latest data rules out the possibility that in the region 20-40 AU of the Solar System an anomalous force field inducing a constant and radial acceleration with those characteristics affects the motion of the major planets.

Iorio, Lorenzo; Giudice, Giuseppe

2006-07-01

172

Orbit Determination of the Lunar Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

We present the results on precision orbit determination from the radio science investigation of the Lunar Reconnaissance Orbiter (LRO) spacecraft. We describe the data, modeling and methods used to achieve position knowledge several times better than the required 50-100m (in total position), over the period from 13 July 2009 to 31 January 2011. In addition to the near-continuous radiometric tracking data, we include altimetric data from the Lunar Orbiter Laser Altimeter (LOLA) in the form of crossover measurements, and show that they strongly improve the accuracy of the orbit reconstruction (total position overlap differences decrease from approx.70m to approx.23 m). To refine the spacecraft trajectory further, we develop a lunar gravity field by combining the newly acquired LRO data with the historical data. The reprocessing of the spacecraft trajectory with that model shows significantly increased accuracy (approx.20m with only the radiometric data, and approx.14m with the addition of the altimetric crossovers). LOLA topographic maps and calibration data from the Lunar Reconnaissance Orbiter Camera were used to supplement the results of the overlap analysis and demonstrate the trajectory accuracy.

Mazarico, Erwan; Rowlands, D. D.; Neumann, G. A.; Smith, D. E.; Torrence, M. H.; Lemoine, F. G.; Zuber, M. T.

2011-01-01

173

Family of Orbiters  

NASA Technical Reports Server (NTRS)

This image shows the paths of three spacecraft currently in orbit around Mars, as well as the path by which NASA's Phoenix Mars Lander will approach and land on the planet. The t-shaped crosses show where the orbiters will be when Phoenix enters the atmosphere, while the x-shaped crosses show their location at landing time.

All three orbiters, NASA's Mars Reconnaissance Orbiter, NASA's Mars Odyssey and the European Space Agency's Mars Express, will be monitoring Phoenix during the final steps of its journey to the Red Planet.

Phoenix will land just south of Mars's north polar ice cap.

2008-01-01

174

Orbital Debris: A Chronology  

NASA Technical Reports Server (NTRS)

This chronology covers the 37-year history of orbital debris concerns. It tracks orbital debris hazard creation, research, observation, experimentation, management, mitigation, protection, and policy. Included are debris-producing, events; U.N. orbital debris treaties, Space Shuttle and space station orbital debris issues; ASAT tests; milestones in theory and modeling; uncontrolled reentries; detection system development; shielding development; geosynchronous debris issues, including reboost policies: returned surfaces studies, seminar papers reports, conferences, and studies; the increasing effect of space activities on astronomy; and growing international awareness of the near-Earth environment.

Portree, Davis S. F. (Editor); Loftus, Joseph P., Jr. (Editor)

1999-01-01

175

Long-Period Meteor Streams and the Dispersion of Semimajor Axes of Meteor Orbits  

NASA Astrophysics Data System (ADS)

The present work is based on an analysis of a large statistical sample of meteor orbits collected in the Japanese shower catalogue (SonotaCo 2009, WGN, 37, 55) of 114280 video observed meteors. The shower meteor data were selected and analysed with the aim of determining the orbits' distribution in major meteor streams with heliocentric velocities close to the parabolic limit, in which the errors in the velocity determination correspond to large differences in the reciprocal semimajor axis, 1/a. The contribution of the real dispersion of the semimajor axes, a, can be deduced from the high proportion of hyperbolic orbits in the analysed streams, where an excess over the parabolic value can be regarded as being entirely due to measurement errors. The orbital dispersion described by the median absolute deviation in terms of 1/a was found to be ±0.083 AU-1 for the Leonids and ±0.080 AU-1 for the Orionids, and slightly smaller for the Perseid and Lyrid meteor streams (±0.055 and ±0.047 AU-1). The proximity of the parabolic limit caused a strong influence of observational effects; however, a significant contribution of the real dispersion is involved.

Hajduková, Mária, Jr.

2013-06-01

176

Congenital orbital encephalocele, orbital dystopia, and exophthalmos.  

PubMed

We present here an exceedingly rare variant of a nonmidline basal encephalocele of the spheno-orbital type, and this was accompanied with orbital dystopia in a 56-year-old man. On examination, his left eye was located more inferolaterally than his right eye, and the patient said this had been this way since his birth. The protrusion of his left eye was aggravated when he is tired. His naked visual acuity was 0.7/0.3, and the ocular pressure was 14/12 mm Hg. The exophthalmometry was 10/14 to 16 mm. His eyeball motion was not restricted, yet diplopia was present in all directions. The distance from the midline to the medial canthus was 20/15 mm. The distance from the midline to the midpupillary line was 35/22 mm. The vertical dimension of the palpebral fissure was 12/9 mm. The height difference of the upper eyelid margin was 11 mm, and the height difference of the lower eyelid margin was 8 mm. Facial computed tomography and magnetic resonance imaging showed left sphenoid wing hypoplasia and herniation of the left anterior temporal pole and dura mater into the orbit, and this resulted into left exophthalmos and encephalomalacia in the left anterior temporal pole. To the best of our knowledge, our case is the second case of basal encephalocele and orbital dystopia. PMID:22801176

Hwang, Kun; Kim, Han Joon

2012-07-01

177

Planetary Orbit Simulator  

NSDL National Science Digital Library

This web page from the University of Nebraska contains a simulation of a planetary orbit. The visitor can control the size of the orbit and the eccentricity. The simulation shows velocity and acceleration factors continually. Each of Kepler's three laws has a separate section, with different display options to illustrate each law.

178

Titan Orbiter Aerorover Mission  

NASA Technical Reports Server (NTRS)

We propose a combined Titan orbiter and Titan Aerorover mission with an emphasis on both in situ and remote sensing measurements of Titan's surface, atmosphere, ionosphere, and magnetospheric interaction. The biological aspect of the Titan environment will be emphasized by the mission (i.e., search for organic materials which may include simple organics to 'amono' analogues of amino acids and possibly more complex, lightening detection and infrared, ultraviolet, and charged particle interactions with Titan's surface and atmosphere). An international mission is assumed to control costs. NASA will provide the orbiter, launch vehicle, DSN coverage and operations, while international partners will provide the Aerorover and up to 30% of the cost for the scientific instruments through collaborative efforts. To further reduce costs we propose a single PI for orbiter science instruments and a single PI for Aerorover science instruments. This approach will provide single command/data and power interface between spacecraft and orbiter instruments that will have redundant central DPU and power converter for their instruments. A similar approach could be used for the Aerorover. The mission profile will be constructed to minimize conflicts between Aerorover science, orbiter radar science, orbiter radio science, orbiter imaging science, and orbiter fields and particles (FP) science. Additional information is contained in the original extended abstract.

Sittler Jr., E. C.; Acuna, M.; Burchell, M. J.; Coates, A.; Farrell, W.; Flasar, M.; Goldstein, B. E.; Gorevan, S.; Hartle, R. E.; Johnson, W. T. K.

2001-01-01

179

Orbital trapdoor fractures  

PubMed Central

Orbital trapdoor fractures are commonly encountered in children. Awareness of trapdoor fractures is of particular importance. This is because early recognition and treatment are necessary to prevent permanent motility abnormities. In this article, we will provide a brief overview of orbital fractures. The clinical and radiographic features of trapdoor fractures will then be reviewed, followed by a discussion on their proper management. PMID:23961006

Phan, Laura T.; Jordan Piluek, W.; McCulley, Timothy J.

2012-01-01

180

Focus on Orbital Physics  

Microsoft Academic Search

The quest for a microscopic understanding of the physical properties of transition metal oxides with orbital degeneracy (`orbital physics') is currently at the forefront of solid-state physics. The field was kicked off nearly 50 years ago by a remarkable pair of papers. In the first, Wollan and Koehler reported using the newly developed technique of neutron scattering to elucidate the

Bernhard Keimer; Andrzej M Oles

2004-01-01

181

Mars Climate Orbiter  

NASA Technical Reports Server (NTRS)

The purpose of this mission is to study the climate history and the water distribution of Mars. Beautiful panoramic views of the shuttle on the launch pad, engine ignition, Rocket launch, and the separation and burnout of the Solid Rocket Boosters are shown. The footage also includes an animation of the mission. Detailed views of the path that the Orbiter traversed were shown. Once the Orbiter lands on the surface of Mars, it will dig a six to eight inch hole and collect samples from the planets' surface. The animation also included the prospective return of the Orbiter to Earth over the desert of Utah. The remote sensor on the Orbiter helps in finding the exact location of the Orbiter so that scientists may collect the sample and analyze it.

1998-01-01

182

Orbital Debris Mitigation  

NASA Technical Reports Server (NTRS)

Policies on limiting orbital debris are found throughout the US Government, many foreign space agencies, and as adopted guidelines in the United Nations. The underlying purpose of these policies is to ensure the environment remains safe for the operation of robotic and human spacecraft in near- Earth orbit. For this reason, it is important to consider orbital debris mitigation during the design of all space vehicles. Documenting compliance with the debris mitigation guidelines occurs after the vehicle has already been designed and fabricated for many CubeSats, whereas larger satellites are evaluated throughout the design process. This paper will provide a brief explanation of the US Government Orbital Debris Mitigation Standard Practices, a discussion of international guidelines, as well as NASA's process for compliance evaluation. In addition, it will discuss the educational value of considering orbital debris mitigation requirements as a part of student built satellite design.

Kelley, R. L.; Jarkey, D. R.; Stansbery, G.

2014-01-01

183

Orbital metastatic osteosarcoma.  

PubMed

At an estimated incidence of 2 cases per million persons per year, osteosarcoma is the most common primary malignant bone tumor in children and adults, excluding hematopoietic intraosseous tumors. Orbital metastases of osteosarcoma are very rare. Only 5 cases of orbital metastasis of osteosarcoma previously reported in the literature. We report the case of a 19-year-old man with known history of osteosarcoma of right distal femur who presented with acute visual loss and progressive protrusion of his left eye. Orbital CT scan and MRI revealed orbital mass eroding orbital walls and intracranial invasion. He underwent superotemporal orbitotomy for debulking of orbital mass. Histopathological examination (HPE) of the specimen was reported as metastatic osteosarcoma with extensive tumor necrosis. Then he underwent adjuvant chemotherapy and palliative radiotherapy. Although orbital metastasis of osteosarcoma is a rare event, it seems it has had an increasing trend recently. so, making efforts to palliate the patient's symptoms by multidisciplinary teamwork and proper interaction among ophthalmologist, orthopedic surgeons and oncologists is necessary. PMID:25644802

Rajabi, Mohammad Taher; Saeedi-Anari, Ghasem; Ramezani, Farshid; Tabatabaie, Seyed-Ziaeddin; Rajabi, Mohammad Bagher; Asadi Amoli, Fahimeh

2015-02-01

184

Harmonically excited orbital variations  

SciTech Connect

Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

Morgan, T.

1985-08-06

185

Orbit Stabilization of Nanosat  

SciTech Connect

An algorithm is developed to control a pulsed {Delta}V thruster on a small satellite to allow it to fly in formation with a host satellite undergoing time dependent atmospheric drag deceleration. The algorithm uses four short thrusts per orbit to correct for differences in the average radii of the satellites due to differences in drag and one thrust to symmetrize the orbits. The radial difference between the orbits is the only input to the algorithm. The algorithm automatically stabilizes the orbits after ejection and includes provisions to allow azimuthal positional changes by modifying the drag compensation pulses. The algorithm gives radial and azimuthal deadbands of 50 cm and 3 m for a radial measurement accuracy of {+-} 5 cm and {+-} 60% period variation in the drag coefficient of the host. Approaches to further reduce the deadbands are described. The methodology of establishing a stable orbit after ejection is illustrated in an appendix. The results show the optimum ejection angle to minimize stabilization thrust is upward at 86{sup o} from the orbital velocity. At this angle the stabilization velocity that must be supplied by the thruster is half the ejection velocity. An ejection velocity of 0.02 m/sat 86{sup o} gives an azimuthal separation after ejection and orbit stabilization of 187 m. A description of liquid based gas thrusters suitable for the satellite control is included in an appendix.

JOHNSON,DAVID J.

1999-12-01

186

OL- ORBITAL LIFETIME PROGRAM  

NASA Technical Reports Server (NTRS)

The Orbital Lifetime (OL) program analyzes the long-term motion of Earth-orbiting spacecraft at altitudes of up to 2500 kilometers. It models perturbations to the orbit caused by solar radiation pressure, atmospheric drag, and gravitational effects due to the sun, the moon, and Earth oblateness. OL can be used to predict the orbital lifetime and decay rate of a satellite. The atmospheric density models used in OL are the U.S. Standard Atmosphere for altitudes below 90 km and the Jacchia model for altitudes above 90 km. The Jacchia model requires solar flux and geomagnetic index for the date of orbit. An input file containing these values for 1984 to 1998 is supplied with the OL package. The solar radiation pressure calculations in OL will predict the amount of time a spacecraft is subjected to the Earth's shadow. Input to OL includes spacecraft physical characteristics, initial orbit parameters, and launch date/time. OL calculates time histories of the orbital elements, total lifetime, and decay rates. A spacecraft is considered 'down' at an altitude of 64 km. OL also generates a file of plot data which can be input to a user-supplied graphics program for lifetime plots of altitude against time. OL is written in FORTRAN 77 for interactive or batch execution and has been implemented on a DEC VAX series computer operating under VMS. This program was developed in 1985.

Orr, L. H.

1994-01-01

187

External Resource: What is orbit?  

NSDL National Science Digital Library

A 5-8 NASA Education reference answering the question, " What is orbit?" Topics include: satellite, ecliptic plane, perigee, apogee, escape velocity, geosynchronous, polar orbits, and low Earth orbit.

1900-01-01

188

Orbital Debris Environment Monitor (ODEM)  

NASA Technical Reports Server (NTRS)

Viewgraphs on orbital debris environmental monitor (ODEM) are presented. Topics covered include: Long Duration Exposure Facility (LDEF); interplanetary dust experiment; orbital debris clouds; mapping and modeling of orbital debris clouds; and solar maximum mission spacecraft.

Oliver, John P.

1992-01-01

189

Working in orbit and beyond  

SciTech Connect

This book contains papers presented at a conference on the challenges for space medicine. Topics covered include radiation hazards in low earth orbit, polar orbit, geosynchronous orbit, and deep space.

Lorr, D.B. (Space Medicine Systems, Inc. (US)); Garshnek, V. (George Washington Univ., Washington, DC (US)); Cadoux, C. (Union Memorial Hospital, Baltimore, MD (US))

1989-01-01

190

Prototyping LHC Orbit Control  

E-print Network

Orbit correction consists in adjusting the strengths of the corrector magnets to make the measured beam position match a predefined reference. In the LHC, this involves around 2000 sensors and more than 1000 actuators that are distributed along both rings. The orbit correction scheme should be able to compensate for very slow orbit drifts in the range of a 10-2 Hz but also for fast motions (vibrations) up to 1 Hz. In this paper we investigate correction schemes that could be used in either case. The choice of design formalisms is based on the experience we gained with the SPS and the LEP.

Wijnands, Thijs; Srinivasan, B

2002-01-01

191

Removal of orbital debris  

NASA Technical Reports Server (NTRS)

The several methods presently identified for the reduction of orbital debris populations are broadly classifiable as either preventive or remedial, and fall within distinctive operational regimes. For all particles, (1) in the 250-2000-km altitude band, intelligent sweepers may be used; (2) for large objects, in the 80-250-km altitude band, orbital decay renders removal impractical; (3) for the 250-750-km altitude band, deorbit devices should be used; (4) for 750-2500-km altitude, OMV rendezvous for propulsive deorbit package attachment is foreseeable; and beyond 2500 km, (5) propulsive escape from earth orbit is required.

Petro, Andrew J.; Talent, David L.

1989-01-01

192

Orbit Determination Issues for Libration Point Orbits  

NASA Technical Reports Server (NTRS)

Libration point mission designers require knowledge of orbital accuracy for a variety of analyses including station keeping control strategies, transfer trajectory design, and formation and constellation control. Past publications have detailed orbit determination (OD) results from individual libration point missions. This paper collects both published and unpublished results from four previous libration point missions (ISEE (International Sun-Earth Explorer) -3, SOHO (Solar and Heliospheric Observatory), ACE (Advanced Composition Explorer) and MAP (Microwave Anisotropy Probe)) supported by Goddard Space Flight Center's Guidance, Navigation & Control Center. The results of those missions are presented along with OD issues specific to each mission. All past missions have been limited to ground based tracking through NASA ground sites using standard range and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using seaboard attitude sensors and the use of the Very Long Baseline Interferometry (VLBI) measurement Delta Differenced One-Way Range (DDOR). Both options potentially enable missions to reduce coherent dedicated tracking passes while maintaining orbital accuracy. With the increased projected loading of the DSN (Deep Space Network), missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

193

S1) The Orbital Dynamics Calculations. S2) Collisional and Dynamical Depletion Evolution Model (CoDDEM) Calculations.  

E-print Network

particle if it either impacted a planet, or reached a heliocentric distance greater than 15 AU or less than any particle that impacted a planet, became Mars-crossing, reached a heliocentric distance of 15 AU

Morbidelli, Alessandro

194

Light's Orbital Angular Momentum  

Microsoft Academic Search

The realization that light beams can have quantized orbital angular momentum in addition to spin angular momentum has led, in recent years, to novel experiments in quantum mechanics and new methods for manipulating microparticles.

Miles Padgett; Johannes Courtial; Les Allen

2004-01-01

195

Tethered orbital refueling study  

NASA Technical Reports Server (NTRS)

One of the major applications of the space station will be to act as a refueling depot for cryogenic-fueled space-based orbital transfer vehicles (OTV), Earth-storable fueled orbit maneuvering vehicles, and refurbishable satellite spacecraft using hydrazine. One alternative for fuel storage at the space station is a tethered orbital refueling facility (TORF), separated from the space station by a sufficient distance to induce a gravity gradient force that settles the stored fuels. The technical feasibility was examined with the primary focus on the refueling of LO2/LH2 orbital transfer vehicles. Also examined was the tethered facility on the space station. It was compared to a zero-gravity facility. A tethered refueling facility should be considered as a viable alternative to a zero-gravity facility if the zero-gravity fluid transfer technology, such as the propellant management device and no vent fill, proves to be difficult to develop with the required performance.

Fester, Dale A.; Rudolph, L. Kevin; Kiefel, Erlinda R.; Abbott, Peter W.; Grossrode, Pat

1986-01-01

196

orbit.ps  

E-print Network

consist of an arbitrary number of troughs are found numerically. The bifurca- ... Key words: water wave, Boussinesq system, traveling wave, homoclinic orbit,. multi-pulsed solution ... But to the best of my knowledge, there is no result regarding.

197

Imaging in orbital trauma  

PubMed Central

Orbital trauma is one of the most common reasons for ophthalmology specialty consultation in the emergency department setting. We survey the literature from 1990 to present to describe the role of computed tomography (CT), magnetic resonance imaging (MRI) and their associated angiography in some of the most commonly encountered orbital trauma conditions. CT orbit can often detect certain types of foreign bodies, lens dislocation, ruptured globe, choroidal or retinal detachments, or cavernous sinus thrombosis and thus complement a bedside ophthalmic exam that can sometimes be limited in the setting of trauma. CT remains the workhorse for acute orbital trauma owing to its rapidity and ability to delineate bony abnormalities; however MRI remains an important modality in special circumstances such as soft tissue assessment or with organic foreign bodies. PMID:23961028

Lin, Ken Y.; Ngai, Philip; Echegoyen, Julio C.; Tao, Jeremiah P.

2012-01-01

198

Aerobraking orbital transfer vehicle  

NASA Technical Reports Server (NTRS)

An aerobraking orbital transfer vehicle which includes an aerobraking device which also serves as a heat shield in the shape of a raked-off elliptic or circular cone with a circular or elliptical base, and with an ellipsoid or other blunt shape nose. The aerobraking device is fitted with a toroid-like skirt and is integral with the support structure of the propulsion system and other systems of the space vehicle. The vehicle is intended to be transported in components to a space station in lower earth orbit where it is assembled for use as a transportation system from low earth orbit to geosynchronous earth orbit and return. Conventional guidance means are included for autonomous flight.

Scott, Carl D. (Inventor); Nagy, Kornel (Inventor); Roberts, Barney B. (Inventor); Ried, Robert C. (Inventor); Kroll, Kenneth R. (Inventor); Gamble, Joe (Inventor)

1989-01-01

199

Optical lattices: Orbital dance  

NASA Astrophysics Data System (ADS)

Emulating condensed-matter physics with ground-state atoms trapped in optical lattices has come a long way. But excite the atoms into higher orbital states, and a whole new world of exotic states appears.

Lewenstein, Maciej; Liu, W. Vincent

2011-02-01

200

Indian Mars Orbiter Mission  

NASA Astrophysics Data System (ADS)

The Mars Orbiter Mission (MOM) is the first interplanetary mission of India launched by Indian Polar Satellite Launch Vehicle (PSLV-XL) on 5 November 2013. It departed from Earth's orbit on Dec. 1, 2013, on its 300-days journey to Mars. MOM will reach Mars on Sept. 24, 2014. The orbit of MOM around Mars is highly elliptical with periapsis ~370 km and apoapsis ~80000 km, inclination 151 degree, and orbital period 3.15 sols. The spacecraft mass is 1350 kg, with dry mass of 500 kg and science payload mass of 14 kg. The spacecraft carries five science payloads, namely: Methane Sensor for Mars (MSM), Mars Colour Camera (MCC), Lyman Alpha Photometer (LAP), Mars Exospheric Neutral Composition Analyzer (MENCA), TIR Imaging Spectrometer (TIS). This paper will present the details of the instruments, observation plan, and expected science.

Bhardwaj, Anil

201

Optical orbital debris spotter  

NASA Astrophysics Data System (ADS)

The number of man-made debris objects orbiting the Earth, or orbital debris, is alarmingly increasing, resulting in the increased probability of degradation, damage, or destruction of operating spacecraft. In part, small objects (<10 cm) in Low Earth Orbit (LEO) are of concern because they are abundant and difficult to track or even to detect on a routine basis. Due to the increasing debris population it is reasonable to assume that improved capabilities for on-orbit damage attribution, in addition to increased capabilities to detect and track small objects are needed. Here we present a sensor concept to detect small debris with sizes between approximately 1.0 and 0.01 cm in the vicinity of a host spacecraft for near real time damage attribution and characterization of dense debris fields and potentially to provide additional data to existing debris models.

Englert, Christoph R.; Bays, J. Timothy; Marr, Kenneth D.; Brown, Charles M.; Nicholas, Andrew C.; Finne, Theodore T.

2014-11-01

202

Habitability study shuttle orbiter  

NASA Technical Reports Server (NTRS)

Studies of the habitability of the space shuttle orbiter are briefly summarized. Selected illustrations and descriptions are presented for: crew compartment, hygiene facilities, food system and galley, and storage systems.

1972-01-01

203

Report on orbital debris  

NASA Technical Reports Server (NTRS)

The success of space endeavors depends upon a space environment sufficiently free of debris to enable the safe and dependable operation of spacecraft. An environment overly cluttered with debris would threaten the ability to utilize space for a wide variety of scientific, technological, military, and commercial purposes. Man made space debris (orbital debris) differs from natural meteoroids because it remains in earth orbit during its lifetime and is not transient through the space around the Earth. The orbital debris environment is considered. The space environment is described along with sources of orbital debris. The current national space policy is examined, along with ways to minimize debris generation and ways to survive the debris environment. International efforts, legal issues and commercial regulations are also examined.

1989-01-01

204

Pediatric Orbital Fractures  

PubMed Central

It is wise to recall the dictum “children are not small adults” when managing pediatric orbital fractures. In a child, the craniofacial skeleton undergoes significant changes in size, shape, and proportion as it grows into maturity. Accordingly, the craniomaxillofacial surgeon must select an appropriate treatment strategy that considers both the nature of the injury and the child's stage of growth. The following review will discuss the management of pediatric orbital fractures, with an emphasis on clinically oriented anatomy and development. PMID:24436730

Oppenheimer, Adam J.; Monson, Laura A.; Buchman, Steven R.

2013-01-01

205

Satellites Orbiting Earth  

NSDL National Science Digital Library

In recent years, there has been a push to better understand how Earth works as a system- how land, oceans, air, and life all interact. Satellites in orbit around Earth are a fast and efficient way of gathering remotely sensed data about the planet as a whole. This animated video shows the orbital paths of the satellites in the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS), a collection of satellites that work together to study Earth on a wide scale.

206

A tapestry of orbits  

SciTech Connect

In this book, the author describes how orbital research developed to yield a rich harvest of knowledge about the earth and its atmosphere. King-Hele relates a personal account of this research based on analysis of satellite orbits between 1957 and 1990 conducted from the Royal Aircraft Establishment in Farnborough England. The early research methods used before the launch of Sputnik in 1957 are discussed.

King-Hele, D.

1992-01-01

207

The Lunar Orbital Prospector  

NASA Technical Reports Server (NTRS)

The establishment of lunar bases will not end the need for remote sensing of the lunar surface by orbiting platforms. Human and robotic surface exploration will necessarily be limited to some proximate distance from the support base. Near real-time, high-resolution, global characterization of the lunar surface by orbiting sensing systems will continue to be essential to the understanding of the Moon's geophysical structure and the location of exploitable minerals and deposits of raw materials. The Lunar Orbital Prospector (LOP) is an orbiting sensing platform capable of supporting a variety of modular sensing packages. Serviced by a lunar-based shuttle, the LOP will permit the exchange of instrument packages to meet evolving mission needs. The ability to recover, modify, and rotate sensing packages allows their reuse in varying combinations. Combining this flexibility with robust orbit modification capabilities and near real-time telemetry links provides considerable system responsiveness. Maintenance and modification of the LOP orbit are accomplished through use of an onboard propulsion system that burns lunar-supplied oxygen and aluminum. The relatively low performance of such a system is more than compensated for by the elimination of the need for Earth-supplied propellants. The LOP concept envisions a continuous expansion of capability through the incorporation of new instrument technologies and the addition of platforms.

Redd, Frank J.; Cantrell, James N.; Mccurdy, Greg

1992-01-01

208

Rotational Disruption of Comets with Parabolic Orbits  

NASA Astrophysics Data System (ADS)

One of the most fundamental problems in planetary science is the natural lifetime of comets, which is limited by several processes, most notably by spontaneous disruption of the nucleus. While the underlying mechanism is uncertain, rapid rotation is often suspected. To address this problem, I derived the probability of rotational disruption, and investigated it for comets with parabolic orbits as a function of perihelion distance and nucleus size for a range of input parameters. The disruption probability is defined as the ratio of expected change in the rotation rate to the allowable span of the rotation rate, the latter being limited by the critical rotation rate (prograde and retrograde), which I adopted from Davidsson (2001, Icarus 149, 375). The expected change in the rotation rate, resulting from the action of torques generated by mass loss, is calculated following the standard approach (e.g. Drahus et al. 2011, ApJL 734, L4, and ref. therein), but taking into account the suspected decrease of the net torque with an increasing active fraction of the nucleus (Jewitt 1997, EM&P 79, 35; Samarasinha & Mueller 2013, ApJL 775, L10). The sublimation flux is obtained from the standard energy balance equation (e.g. Cowan & A’Hearn 1979, M&P 21, 155), but I also take into account extinction of sunlight in the dust coma. I find that close to the Sun coma transmission steeply decreases with a decreasing heliocentric distance, resulting in the sublimation flux at a remarkably constant level, and also that coma transmission decreases with an increasing nucleus size, both properties being critically important in the calculation of sublimation flux for large sungrazers. The obtained rotational-disruption probability features several interesting properties. It has a well-defined regime occupied by smaller comets closely approaching the Sun, for which rotational disruption is unavoidable regardless of the original rotation state. Moreover, the probability function offers a very close match to the empirical survival cutoff for long-period comets with perihelia of less than 0.5 AU (Bortle 1991, ICQ 13, 89), independently suggesting that rotational disruption is the primary mechanism responsible for the destruction of comets.

Drahus, Michal

2014-11-01

209

The Tajikistan superbolide of July 23, 2008. I. Trajectory, orbit, and preliminary fall data  

NASA Astrophysics Data System (ADS)

The results of the atmospheric trajectory, radiant, heliocentric orbit, and preliminary strewn field calculations for an extremely bright slow-moving fireball are presented. In the evening hours of July 23, 2008, a bright object entered Earth's atmosphere over Tajikistan. The fireball had a -20.3 maximum absolute magnitude and a spectacularly long persistent dust trail remained visible over a widespread region of Tajikistan for about 28 minutes after sunset. The fireball was also recorded by a visible-light satellite system at 14 h 45 min 25 s UT, and the dust trail was imaged by video and photocameras. A unique aspect of this event is that it was detected by two infrasound and five seismic stations too. The bolide was first recorded at a height of 38.2 km, reached its maximum brightness at a height of 35.0 km, and finished at a height of 19.6 km. The first breakup occurred under an aerodynamic pressure of approximately 1.6 MPa, similar to the values derived for breakups of the scarcely reported meteorite-dropping bolides. The fireball's trajectory and dynamic results suggest that meteorite survival is likely. The meteoroid followed an Apollo-like asteroid orbit comparable to those derived for previously recovered meteorites with accurately known orbits.

Konovalova, Natalia A.; Madiedo, Jose M.; Trigo-Rodríguez, Josep M.

2013-12-01

210

[Orbital complications of sinusitis].  

PubMed

Orbital complications categorised by Chandler are emergency. They need early diagnosis and agresive treatment. Stage and origin of orbital complications are identified by rhinoendoscopy, ophtalmologic examination and CT of orbite and paranasal sinuses. Periorbital cellulitis and early stage of orbital cellulitis can be treated conservatively with i. v. antibiotics. Monitoring of laboratory parameters and ophtalmologic symptoms is mandatory. Lack of improvement or worsening of symptoms within 24-48 hours and advanced stages of orbital complications are indicated for surgery. The purpose of the study is to evaluate epidemiology, clinical features and management of sinogenic orbital complications. Retrospective data of 8 patients with suspicion of orbital complication admited to hospital from 2008 to 2013 were evaluated. Patients were analyzed in terms of gender, age, CT findings, microbiology, clinical features, stage and treatment. Male and female were afected in rate 1,66:1. Most of patients were young adult in 3rd. and 4th. decade of life (62,5 %). Acute and chronic sinusitis were cause of orbital complication in the same rate. The most common origin of orbital complication was ethmoiditis (62,5 %), than maxillary (25 %) and frontal (12,5 %) sinusitis. Polysinusitis with affection of ethmoidal, maxillary and frontal sinuses (75 %) was usual CT finding. Staphylococcus epidermidis and Staphylococcus aureus were etiological agens in half of cases. Periorbital oedema (100 %), proptosis, chemosis (50 %), diplopia and glaucoma (12,5 %) were observed. Based on examinations, diagnosis of periorbital oedema/preseptal cellulitis was made in 3 (37,5 %), orbital cellulitis in 3 (37,5 %) and subperiosteal abscess in 2 cases (25 %). All patients underwent combined therapy - i. v. antibiotics and surgery within 24 hours. Eradication of disease from ostiomeatal complex (OMC), drainage of affected sinuses and drainage of subperiosteal abscess were done via fuctional endonasal endoscopic surgery (FEES). In case of superior subperiosteal abscess, combined endonasal and external approach (external orbitotomy) was needed. Combined therapy facilitated quick improvement of local and systematic symptoms. Average time of hospitalisation was 7 days. Early diagnosis and agresive combined therapy prevent loss of vision and life threatening complications. PMID:25640234

Šucha?, M; Hor?ák, M; Kaliarik, L; Krempaská, S; Koštialová, T; Kova?, J

2014-12-01

211

Mars Geoscience Orbiter and Lunar Geoscience Orbiter  

NASA Technical Reports Server (NTRS)

The feasibility of using the AE/DE Earth orbiting spacecraft design for the LGO and/or MGO missions was determined. Configurations were developed and subsystems analysis was carried out to optimize the suitability of the spacecraft to the missions. The primary conclusion is that the basic AE/DE spacecraft can readily be applied to the LGO mission with relatively minor, low risk modifications. The MGO mission poses a somewhat more complex problem, primarily due to the overall maneuvering hydrazine budget and power requirements of the sensors and their desired duty cycle. These considerations dictate a modification (scaling up) of the structure to support mission requirements.

Fuldner, W. V.; Kaskiewicz, P. F.

1983-01-01

212

LAGEOS orbit and solar eclipses  

Microsoft Academic Search

The objective was to assess the importance of solar eclipses on Lageos' orbit. Solar radiation pressure perturbs the orbit of the Lageos satellite. The GEODYN orbit determination computer program includes solar radiation pressure as one of the forces operating on the satellite as it integrates the orbit. GEODYN also takes into account the extinction of sunlight when Lageos moves into

D. P. Rubincam

1984-01-01

213

Gravity and Orbits  

NSDL National Science Digital Library

The Gravity and Orbits SciPack explores concepts related to Earth's universal gravitation and how gravity affects the universe around us. The focus is on Standards and Benchmarks related to universal gravitation including variables that influence the amount of gravitational force and how gravity governs the motion of the solar system.In addition to comprehensive inquiry-based learning materials tied to Science Education Standards and Benchmarks, the SciPack includes the following additional components:? Pedagogical Implications section addressing common misconceptions, teaching resources and strand maps linking grade band appropriate content to standards. ? Access to one-on-one support via e-mail to content "Wizards".? Final Assessment which can be used to certify mastery of the concepts.Learning Outcomes:Gravity and Orbits: Universal Gravitation? Identify gravity as an attractive force associated with all objects, including less intuitive examples (such as soda cans and pencils).? Recognize some examples of phenomena that are the result of Earth's gravity and objects and structures in the universe in general.? Reject the idea that Earth's gravity is an effect of air pushing down toward the surface.? Recognize that gravitational force does not require air (or any other substance) as a medium to act.? Describe gravitational force as a mutual attraction, rather than as one object pulling on another.Gravity and Orbits: Gravitational Force? Identify variables that affect the strength of the gravitational force acting between any two objects.? Provide a quantitative description of the relationship between the mass of two object and the gravitational force between them.? Provide a qualitative description of the relationship between the mass of two objects and the gravitational force between them.? Provide a quantitative description of the relationship between distance and gravitational force. ? Provide a qualitative description of the inverse square relationship.? Recognize the effect of air resistance on object falling near Earth's surface, and thus be able to explain why two objects with different masses, at the same distance from Earth's surface, will have equal accelerations if air resistance is ignored. Gravity and Orbits: Orbits? Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.? Explain how an object orbits a planet in terms of trajectories and free fall.? Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2007-03-21

214

Mars Telecommunications Orbiter, Artist's Concept  

NASA Technical Reports Server (NTRS)

This illustration depicts a concept for NASA's Mars Telecommunications Orbiter in flight around Mars. The orbiter is in development to be the first spacecraft with a primary function of providing communication links while orbiting a foreign planet. The project's plans call for launch in September 2009, arrival at Mars in August 2010 and a mission of six to 10 years while in orbit. Mars Telecommunication Orbiter would serve as the Mars hub for an interplanetery Internet, greatly increasing the information payoff from other future Mars missions. The mission is designed to orbit Mars more than 10 times farther from the planet than orbiters dedicated primarily to science. The high-orbit design minimizes the time that Mars itself blocks the orbiter from communicating with Earth and maximizes the time that the orbiter is above the horizon -- thus capable of communications relay -- for rovers and stationary landers on Mars' surface.

2005-01-01

215

Sedna Orbit Comparisons  

NASA Technical Reports Server (NTRS)

These four panels show the location of the newly discovered planet-like object, dubbed 'Sedna,' which lies in the farthest reaches of our solar system. Each panel, moving counterclockwise from the upper left, successively zooms out to place Sedna in context. The first panel shows the orbits of the inner planets, including Earth, and the asteroid belt that lies between Mars and Jupiter. In the second panel, Sedna is shown well outside the orbits of the outer planets and the more distant Kuiper Belt objects. Sedna's full orbit is illustrated in the third panel along with the object's current location. Sedna is nearing its closest approach to the Sun; its 10,000 year orbit typically takes it to far greater distances. The final panel zooms out much farther, showing that even this large elliptical orbit falls inside what was previously thought to be the inner edge of the Oort cloud. The Oort cloud is a spherical distribution of cold, icy bodies lying at the limits of the Sun's gravitational pull. Sedna's presence suggests that this Oort cloud is much closer than scientists believed.

2004-01-01

216

Indentities Relating Spin-Spin and Orbit-Orbit to Spin-Orbit Interactions  

Microsoft Academic Search

We derive indentities that express spin-spin and orbit-orbit interactions in terms of two-electron spin-orbit matrix elements. They can reduce, in effect, any study of the two-electron Breit-Pauli Hamiltonian for atoms or molecules to one of determining the spin-orbit integrals, thereby considerably unifying and simplifying the whole analysis.

R. L. Matcha; C. W. Kern

1970-01-01

217

Radiation therapy: orbital tumors.  

PubMed

Orbital tumors are rare overall, comprising 0.1% of all tumors and less than 20% of all orbital diseases. Tumors may be benign, locally aggressive, or malignant. Of the malignant tumors, lymphomas and metastases are the most common and are primarily seen in the elderly population. While surgery and chemotherapeutic agents are often employed in the management of these lesions, not all patients are candidates for these therapies. Radiation therapy offers a noninvasive, well-tolerated primary treatment modality, whereby vision-sparing is feasible in many cases. In this chapter, we review an array of non-neoplastic entities and orbital tumors, for which there exists a role for radiation, and the radiotherapeutic techniques and applications in their management. PMID:23989130

Marwaha, Gaurav; Macklis, Roger; Singh, Arun D

2013-01-01

218

Orbit maintenance for low altitude near-circular lunar orbits  

NASA Technical Reports Server (NTRS)

The behavior of low altitude near-circular lunar orbits is a key design issue for some missions in the proposed Space Exploration Initiative. The lunar gravity field strongly perturbs low altitude orbits, so an effective orbit maintenance strategy is needed. This strategy must contend with the long term orbit evolution due to the zonal gravity field. Two possible orbit control scenarios are passive control using a frozen orbit and active orbit control using maneuvers. A maneuver strategy can be designed which optimizes the propellant required for long term orbit sustenance. The long term requirements dominate the total propellant required for orbit control. Additional propellant may be required to offset the impact of medium period gravity field effects. Careful selection of maneuver times and directions, however, can eliminate any medium period penalty.

Cook, Richard A.; Sweetser, Theodore H.

1992-01-01

219

DASTCOM5: A Portable and Current Database of Asteroid and Comet Orbit Solutions  

NASA Astrophysics Data System (ADS)

A portable direct-access database containing all NASA/JPL asteroid and comet orbit solutions, with the software to access it, is available for download (ftp://ssd.jpl.nasa.gov/pub/xfr/dastcom5.zip; unzip -ao dastcom5.zip). DASTCOM5 contains the latest heliocentric IAU76/J2000 ecliptic osculating orbital elements for all known asteroids and comets as determined by a least-squares best-fit to ground-based optical, spacecraft, and radar astrometric measurements. Other physical, dynamical, and covariance parameters are included when known. A total of 142 parameters per object are supported within DASTCOM5. This information is suitable for initializing high-precision numerical integrations, assessing orbit geometry, computing trajectory uncertainties, visual magnitude, and summarizing physical characteristics of the body. The DASTCOM5 distribution is updated as often as hourly to include newly discovered objects or orbit solution updates. It includes an ASCII index of objects that supports look-ups based on name, current or past designation, SPK ID, MPC packed-designations, or record number. DASTCOM5 is the database used by the NASA/JPL Horizons ephemeris system. It is a subset exported from a larger MySQL-based relational Small-Body Database ("SBDB") maintained at JPL. The DASTCOM5 distribution is intended for programmers comfortable with UNIX/LINUX/MacOSX command-line usage who need to develop stand-alone applications. The goal of the implementation is to provide small, fast, portable, and flexibly programmatic access to JPL comet and asteroid orbit solutions. The supplied software library, examples, and application programs have been verified under gfortran, Lahey, Intel, and Sun 32/64-bit Linux/UNIX FORTRAN compilers. A command-line tool ("dxlook") is provided to enable database access from shell or script environments.

Giorgini, Jon D.; Chamberlin, Alan B.

2014-11-01

220

Spiral Orbit Tribometer  

NASA Technical Reports Server (NTRS)

The spiral orbit tribometer (SOT) bridges the gap between full-scale life testing and typically unrealistic accelerated life testing of ball-bearing lubricants in conjunction with bearing ball and race materials. The SOT operates under realistic conditions and quickly produces results, thereby providing information that can guide the selection of lubricant, ball, and race materials early in a design process. The SOT is based upon a simplified, retainerless thrust bearing comprising one ball between flat races (see figure). The SOT measures lubricant consumption and degradation rates and friction coefficients in boundary lubricated rolling and pivoting contacts. The ball is pressed between the lower and upper races with a controlled force and the lower plate is rotated. The combination of load and rotation causes the ball to move in a nearly circular orbit that is, more precisely, an opening spiral. The spiral s pitch is directly related to the friction coefficient. At the end of the orbit, the ball contacts the guide plate, restoring the orbit to its original radius. The orbit is repeatable throughout the entire test. A force transducer, mounted in-line with the guide plate, measures the force between the ball and the guide plate, which directly relates to the friction coefficient. The SOT, shown in the figure, can operate in under ultra-high vacuum (10(exp -9) Torr) or in a variety of gases at atmospheric pressure. The load force can be adjusted between 45 and 450 N. By varying the load force and ball diameter, mean Hertzian stresses between 0.5 and 5.0 GPa can be obtained. The ball s orbital speed range is between 1 and 100 rpm.

Pepper, Stephen V.; Jones, William R., Jr.; Kingsbury, Edward; Jansen, Mark J.

2007-01-01

221

Trajectories and Orbits  

NSDL National Science Digital Library

Materials presented here outline some basic concepts associated with space flight. Users can read about orbits and the difference between an orbit and a trajectory, escape velocities for Earth and some planets, launch velocities and transit times for interplanetary flights, and the effects of time dilation for astronauts travelling at near-light speeds. This is part of the famous Rand corporation study that was commissioned by Congress in 1958 after the Soviet Union stunned the world by launching Sputnik, the world's first artificial satellite.

222

Passive orbital disconnect strut  

NASA Technical Reports Server (NTRS)

The design and test results with a third generation passive orbital disconnect strut (PODS) for space-based cryogenic He dewars are presented. Three pairs of PODS struts support a tank and change lengths in response to gas and temperature changes. A thin wall fiberglass tube is used on the cold disconnect end, which can be operated on the ground or in space. Tests were performed to characterize heat flows across the cold end to a liquid He sink and subsequent vacuum pressure within the He tank. Heat transfer was lower than predicted, suggesting that longer dewar in-orbit lifetimes can be expected with the new PODS.

Parmley, R. T.; Kittel, P.

1984-01-01

223

Design of low-energy transfer from lunar orbit to asteroid in the Sun-Earth-Moon system  

NASA Astrophysics Data System (ADS)

Asteroid exploration trajectories which start from a lunar orbit are investigated in this work. It is assumed that the probe departs from lunar orbit and returns to the vicinity of Earth, then escapes from the Earth by performing a perigee maneuver. A low-energy transfer in Sun-Earth-Moon system is adopted. First, the feasible region of low-energy transfer from lunar orbit to perigee within 5 000km height above the Earth surface in Sun-Earth-Moon system is calculated and analyzed. Three transfer types are found, i.e., large maneuver and fast transfers, small maneuver and fast transfers, and disordered and slow transfers. Most of feasibility trajectories belong to the first two types. Then, the low-energy trajectory leg from lunar orbit to perigee and a heliocentric trajectory leg from perigee to asteroid are patched by a perigee maneuver. The optimal full-transfer trajectory is obtained by exploiting the differential evolution algorithm. Finally, taking 4179 Toutatis asteroid as the target, some low-energy transfer trajectories are obtained and analyzed.

Wang, Ya-Min; Qiao, Dong; Cui, Ping-Yuan

2014-12-01

224

Sedna Orbit Animation  

NASA Technical Reports Server (NTRS)

This animation shows the location of the newly discovered planet-like object, dubbed 'Sedna,' in relation to the rest of the solar system. Starting at the inner solar system, which includes the orbits of Mercury, Venus, Earth, and Mars (all in yellow), the view pulls away through the asteroid belt and the orbits of the outer planets beyond (green). Pluto and the distant Kuiper Belt objects are seen next until finally Sedna comes into view. As the field widens the full orbit of Sedna can be seen along with its current location. Sedna is nearing its closest approach to the Sun; its 10,000 year orbit typically takes it to far greater distances. Moving past Sedna, what was previously thought to be the inner edge of the Oort cloud appears. The Oort cloud is a spherical distribution of cold, icy bodies lying at the limits of the Sun's gravitational pull. Sedna's presence suggests that this Oort cloud is much closer than scientists believed.

2004-01-01

225

Magellan orbits Venus  

NASA Technical Reports Server (NTRS)

Various events surrounding Magellan's orbit of Venus are recounted. Significant events include the successful firing of a solid rocket motor while the spacecraft was behind Venus to transfer it from a solar-centered trajectory to an orbit around the planet. The spacecraft orbits Venus every 3.26 hours at a maximum altitude of 8500 km and minimum altitude of 291 km in an elliptical orbit. The successful August 16 test of the synthetic-aperture radar system is discussed, noting that it produced two strips, each about 20 km x 16,000 km, revealing details as small as 120 m. Two anomalies causing a delay in the start of mapping operations and subsequent breaks in the communication link with earth for 14.5 hours and 17.7 hours are discussed. Protective measures directed from the spacecraft's ROM during breach of contact are listed, and possible causes of the anomalies are suggested, such as solar activity or hardware or software elements, although the actual cause is not yet known.

Mclaughlin, W. I.

1990-01-01

226

Orbital Forces: Student Page  

NSDL National Science Digital Library

This activity teaches students about orbital motions and forces using a tennis ball swung by a ribbon. Students answer the question "What happens when you let the ball go?" Background information, activity procedures, and key words are provided. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

227

Orbital Forces: Teacher Page  

NSDL National Science Digital Library

This activity demonstates orbital motions and forces using a tennis ball swung by a ribbon (this activity should be done outside). The Teacher Page contains background information, tennis ball preparation instructions, and wrap up information. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

228

Orbital physics in RIXS  

NASA Astrophysics Data System (ADS)

In contrast to magnetism, phenomena associated with the orbital degrees of freedom in transition metal oxides had always been considered to be very difficult to observe. However, recently resonant inelastic x-ray scattering (RIXS) has established itself as a perfect probe of the orbital excitations [1] and orbital order [2] in transition metal oxides. Here we give a brief overview of these recent theoretical and experimental advances which have inter alia led to the observation of the separation of the spin and orbital degree of freedom of an electron [1, 3].[4pt] [1] J. Schlappa, K. Wohlfeld, K. J. Zhou, M. Mourigal, M. W. Haverkort, V. N. Strocov, L. Hozoi, C. Monney, S. Nishimoto, S. Singh, A. Revcolevschi, J.-S. Caux, L. Patthey, H. M. Rønnow, J. van den Brink, T. Schmitt, Nature 485, 82 (2012).[0pt] [2] P. Marra, K. Wohlfeld, J. van den Brink, Phys. Rev. Lett. 109, 117401 (2012).[0pt] [3] K. Wohlfeld, M. Daghofer, S. Nishimoto, G. Khaliullin, J. van den Brink, Phys. Rev. Lett. 107, 147201 (2011).

Wohlfeld, Krzysztof; Marra, Pasquale; Grueninger, Markus; Schmitt, Thorsten; van den Brink, Jeroen

2013-03-01

229

Global orbit corrections  

SciTech Connect

There are various reasons for preferring local (e.g., three bump) orbit correction methods to global corrections. One is the difficulty of solving the mN equations for the required mN correcting bumps, where N is the number of superperiods and m is the number of bumps per superperiod. The latter is not a valid reason for avoiding global corrections, since, we can take advantage of the superperiod symmetry to reduce the mN simultaneous equations to N separate problems, each involving only m simultaneous equations. Previously, I have shown how to solve the general problem when the machine contains unknown magnet errors of known probability distribution; we made measurements of known precision of the orbit displacements at a set of points, and we wish to apply correcting bumps to minimize the weighted rms orbit deviations. In this report, we will consider two simpler problems, using similar methods. We consider the case when we make M beam position measurements per superperiod, and we wish to apply an equal number M of orbit correcting bumps to reduce the measured position errors to zero. We also consider the problem when the number of correcting bumps is less than the number of measurements, and we wish to minimize the weighted rms position errors. We will see that the latter problem involves solving equations of a different form, but involving the same matrices as the former problem.

Symon, K.

1987-11-01

230

Lunar Orbit Anomaly  

NASA Astrophysics Data System (ADS)

Independent experiments show a large anomaly in measurements of lunar orbital evolution, with applications to cosmology and the speed of light. The Moon has long been known to be slowly drifting farther from Earth due to tidal forces. The Lunar Laser Ranging Experiment (LLRE) indicates the Moon's semimajor axis increasing at 3.82 ± .07 cm/yr, anomalously high. If the Moon were today gaining angular momentum at this rate, it would have coincided with Earth less than 2 Gyr ago. Study of tidal rhythmites indicates a rate of 2.9 ± 0.6 cm/yr. Historical eclipse observations independently measure a recession rate of 2.82 ± .08 cm/yr. Detailed numerical simulation of lunar orbital evolution predicts 2.91 cm/yr. LLRE differs from three independent experiments by over12 sigma. A cosmology where speed of light c is related to time t by GM=tc^3 has been suggested to predict the redshifts of Type Ia supernovae, and a 4.507034% proportion of baryonic matter. If c were changing in the amount predicted, lunar orbital distance would appear to increase by an additional 0.935 cm/yr. An anomaly in the lunar orbit may be precisely calculated, shedding light on puzzles of 'dark energy'. In Planck units this cosmology may be summarized as M=R=t.Lunar Recession Rate;

Riofrio, L.

2012-12-01

231

KBO orbits for occultations  

NASA Astrophysics Data System (ADS)

The orbits and physical properties of Kuiper Belt Objects (KBOs) provide valuable constraints on the dynamical and environmental evolution of the outer Solar System. Much progress has been made in the past two decades of KBO observations but we still have limited information on physical sizes of these objects. Thermal observations work well (with Spitzer and Herschel) but the dynamically cold classical KBOs (low inclination, low eccentricity near 45 AU) have proven especially challenging with radiometric techniques. This particular class of object is arguably the most primitive (least disturbed) and are a critical component for study. Stellar occultations can provide the missing sizes but to do so we need more objects with better orbits to make these observations feasible. The cold classical objects are also the most likely to have satellites. Getting an occultation diameter on binary objects will permit getting accurate densities since the system mass is known from the satellite orbit. These proposed observations will collect critical astrometry needed to improve the orbits of under- observed KBOs that are candidates for stellar occultation observations. Where possible, known binaries will be given preference for astrometry. This work is part of a NSF-funded pilot project to secure occultation diameters of KBOs.

Buie, Marc

2013-08-01

232

PKUPs Around Orbit Test  

NASA Astrophysics Data System (ADS)

This program is designed to test the idea of multiple PKUPs per viewing interval using the MDRS aperture. The same target will be scheduled in several different patterns with respect to the orbital Day/Night boundary to assess the best method of MDRS operations to get SiC coverage of D/H and other targets.

Blair, William

233

A Neptune Orbiter Mission  

NASA Technical Reports Server (NTRS)

This paper describes the results of new analyses and mission/system designs for a low cost Neptune Orbiter mission. Science and measurement objectives, instrumentation, and mission/system design options are described and reflect an aggressive approach to the application of new advanced technologies expected to be available and developed over the next five to ten years.

Wallace, R. A.; Spilker, T. R.

1998-01-01

234

Orbital Fluid Transfer System  

NASA Technical Reports Server (NTRS)

An automated fluid and power interface system needs to be developed for future space missions which require on orbit consumable replenishment. Current method of fluid transfer require manned vehicles and extravehicular activity. Currently the US does not have an automated capability for consumable transfer on-orbit. This technology would benefit both Space Station and long duration satellites. In order to provide this technology the Automated Fluid Interface System (AFIS) was developed. The AFIS project was an advanced development program aimed at developing a prototype satellite servicer for future space operations. This mechanism could transfer propellants, cryogens, fluids, gasses, electrical power, and communications from a tanker unit to the orbiting satellite. The development of this unit was a cooperative effort between Marshall Space Flight Center in Huntsville, Alabama, and Moog, Inc. in East Aurora, New York. An engineering model was built and underwent substantial development testing at Marshall Space Flight Center (MSFC). While the AFIS is not suitable for spaceflight, testing and evaluation of the AFIS provided significant experience which would be beneficial in building a flight unit. The lessons learned from testing the AFIS provided the foundation for the next generation fluid transfer mechanism, the Orbital Fluid Transfer System (OFTS). The OFTS project was a study contract with MSFC and Moog, Inc. The OFTS was designed for the International Space Station (ISS), but its flexible design could used for long duration satellite missions and other applications. The OFTS was designed to be used after docking. The primary function was to transfer bipropellants and high pressure gases. The other items addressed by this task included propellant storage, hardware integration, safety and control system issues. A new concept for high pressure couplings was also developed. The results of the AFIS testing provided an excellent basis for the OFTS design. The OFTS meet the servicing requirements for ISS and could also provide the automated fluid and power interface system needed for on orbit consumable resupply of spacecraft into the new century.

Johnston, A. S., (Nick); Ryder, Mel; Tyler, Tony R.

1998-01-01

235

CO-ORBITAL OLIGARCHY  

SciTech Connect

We present a systematic examination of the changes in semimajor axis of a protoplanet as it interacts with other protoplanets in the presence of eccentricity dissipation. For parameters relevant to the oligarchic stage of planet formation, dynamical friction keeps the typical eccentricities small and prevents orbit crossing. Interactions at impact parameters greater than several Hill radii cause the protoplanets to repel each other; if the impact parameter is instead much less than the Hill radius, the protoplanets shift slightly in semimajor axis but remain otherwise unperturbed. If the orbits of two or more protoplanets are separated by less than a Hill radius, they are each pushed toward an equilibrium spacing between their neighbors and can exist as a stable co-orbital system. In the shear-dominated oligarchic phase of planet formation, we show that the feeding zones contain several oligarchs instead of only one. Growth of the protoplanets in the oligarchic phase drives the disk to an equilibrium configuration that depends on the mass ratio of protoplanets to planetesimals, {sigma}/{sigma}. Early in the oligarchic phase, when {sigma}/{sigma} is low, the spacing between rows of co-orbital oligarchs are about 5 Hill radii wide, rather than the 10 Hill radii cited in the literature. It is likely that at the end of oligarchy, the average number of co-orbital oligarchs is greater than unity. In the outer solar system, this raises the disk mass required to form the ice giants. In the inner solar system, this lowers the mass of the final oligarchs and requires more giant impacts than previously estimated. This result provides additional evidence that Mars is not an untouched leftover from the oligarchic phase, but must be composed of several oligarchs assembled through giant impacts.

Collins, Benjamin F.; Sari, Re'em [California Institute of Technology, MC 130-33, Pasadena, CA 91125 (United States)], E-mail: bfc@tapir.caltech.edu

2009-04-15

236

Single Frequency GPS Orbit Determination for Low Earth Orbiters  

NASA Technical Reports Server (NTRS)

A number of missions in the future are planning to use GPS for precision orbit determination. Cost considerations and receiver availability make single frequency GPS receivers attractive if the orbit accuracy requirements can be met.

Bertiger, Willy; Wu, Sien-Chong

1996-01-01

237

Unusual sclerosing orbital pseudotumor infiltrating orbits and maxillofacial regions.  

PubMed

Idiopathic orbital pseudotumor (IOP) is a benign inflammatory condition of the orbit without identifiable local or systemic causes. Bilateral massive orbital involvement and extraorbital extension of the IOP is very rare. We present an unusual case of IOP with bilateral massive orbital infiltration extending into maxillofacial regions and discuss its distinctive magnetic resonance imaging (MRI) features that help to exclude other entities during differential diagnoses. PMID:24991481

Toprak, Huseyin; Arala?mak, Ay?e; Y?lmaz, Temel Fatih; Ozdemir, Huseyin

2014-01-01

238

Unusual Sclerosing Orbital Pseudotumor Infiltrating Orbits and Maxillofacial Regions  

PubMed Central

Idiopathic orbital pseudotumor (IOP) is a benign inflammatory condition of the orbit without identifiable local or systemic causes. Bilateral massive orbital involvement and extraorbital extension of the IOP is very rare. We present an unusual case of IOP with bilateral massive orbital infiltration extending into maxillofacial regions and discuss its distinctive magnetic resonance imaging (MRI) features that help to exclude other entities during differential diagnoses. PMID:24991481

Toprak, Huseyin; Arala?mak, Ay?e; Y?lmaz, Temel Fatih; Ozdemir, Huseyin

2014-01-01

239

Close up view of the Orbiter Discovery in the Orbiter ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Close up view of the Orbiter Discovery in the Orbiter Processing Facility at Kennedy Space Center. The view is a detail of the aft, starboard landing gear and a general view of the Thermal Protection System tiles around the landing-gear housing. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

240

Orbit Insertion by Mars Reconnaissance Orbiter (Artist's Concept)  

NASA Technical Reports Server (NTRS)

This is an artist's concept of NASA's Mars Reconnaissance Orbiter during the critical process of Mars orbit insertion. In order to be captured into orbit around Mars, the spacecraft must conduct a 25-minute rocket burn when it is just shy of reaching the planet. As pictured, it will pass under the red planet's southern hemisphere as it begins the insertion burn.

2005-01-01

241

Surgical treatment of orbital cavernomas  

Microsoft Academic Search

BackgroundThere are numerous descriptions for the operative techniques applied in orbital lesions. We present a systematic overview of the surgical approaches, as determined by the location and extension of orbital cavernomas.

Uta Schick; Uwe Dott; Werner Hassler

2003-01-01

242

The Orbital Acceleration Research Experiment  

NASA Technical Reports Server (NTRS)

The hardware and software of NASA's proposed Orbital Acceleration Research Experiment (OARE) are described. The OARE is to provide aerodynamic acceleration measurements along the Orbiter's principal axis in the free-molecular flow-flight regime at orbital attitude and in the transition regime during reentry. Models considering the effects of electromagnetic effects, solar radiation pressure, orbiter mass attraction, gravity gradient, orbital centripetal acceleration, out-of-orbital-plane effects, orbiter angular velocity, structural noise, mass expulsion signal sources, crew motion, and bias on acceleration are examined. The experiment contains an electrostatically balanced cylindrical proofmass accelerometer sensor with three orthogonal sensing axis outputs. The components and functions of the experimental calibration system and signal processor and control subsystem are analyzed. The development of the OARE software is discussed. The experimental equipment will be enclosed in a cover assembly that will be mounted in the Orbiter close to the center of gravity.

Blanchard, R. C.; Hendrix, M. K.; Fox, J. C.; Thomas, D. J.; Nicholson, J.

1986-01-01

243

Flight Paths of Orbiting Satellites  

NSDL National Science Digital Library

This is an activity to help students visualize the relationship of motion, time and space as it relates to objects orbiting the earth. They will be able to track the path of an orbiting object on a globe, plot the path of an orbiting object on a flat world map, and explain that an object orbiting earth on a plane will produce a flight path which appears as wavy lines on the earths surface.

244

Multidisciplinary Management of Orbital Rhabdomyosarcoma  

Microsoft Academic Search

\\u000a Rhabdomyosarcoma (RMS) is the most common orbital malignancy in childhood. Embryonal RMS and alveolar RMS are the two most\\u000a common histologic subtypes of RMS, and embryonal RMS is the most common subtype of orbital RMS. The clinical presentation\\u000a of orbital RMS depends on the tumor location in the orbit. Diagnosis is chiefly made through open biopsy, and complete initial\\u000a tumor

Winston W. Huh; Anita Mahajan

245

Orbiter Servicer Rendezvous Simulation (ORSIM)  

Microsoft Academic Search

Orbiter Servicer Rendezvous Simulation (ORSIM) is an automated tool that simulates sequential transfer maneuvers of an orbital maneuvering vehicle (OMV) transporting orbital replaceable units from a space-based depot, or logistics platform, to higher altitude SDI sdatellites. ORSIM calculates OMV energy expenditures (velocity changes) and event histories for various combinations of user-selected orbital transfer maneuvers. Additionally, ORSIM determines the optimal configuration\\/quantities

Amiel Amato; Mickie D. Hoffman

1987-01-01

246

Orbital myxoma: a case report.  

PubMed

Orbital myxomas are extremely rare tumors. We describe a 75-year old male patient with lower eyelid ectropion and 8-mm of left non-axial proptosis. Orbital CT and MRI revealed a well-demarcated lesion in the lateral quadrant of the orbit. After complete surgical excision, histopathological examination led to the diagnosis of orbital myxoma. The patient was followed-up for 1 year without recurrence. PMID:23560550

Tawfik, Hatem A; Elraey, Haidy Z

2013-06-01

247

Orbit Spaces in Superconductivity  

E-print Network

In the framework of Landau theory of phase transitions one is interested to describe all the possible low symmetry ``superconducting'' phases allowed for a given superconductor crystal and to determine the conditions under which this crystal undergoes a phase transition. These problems are best described and analyzed in the orbit space of the high symmetry group of the ``normal, non-superconducting'' phase of the crystal. In this article it is worked out a simple example concerning superconductivity, that shows the P-matrix method to determine the equations and inequalities defining the orbit space and its stratification. This approach is of general validity and can be used in all physical problems that make use of invariant functions, as long as the symmetry group is compact.

Vittorino Talamini

2006-07-30

248

Lunar Reconnaissance Orbiter  

NSDL National Science Digital Library

Humans have been to the moon numerous times, but the United States is gearing up to do so again with the creation of the Lunar Reconnaissance Orbiter (LRO) mission. With a launch date of October 31, 2008, the goal of the LRO is to obtain "data that will facilitate returning humans safely to the Moon and enable extended stays.� On this site, visitors can learn all of the excellent details about the mission. The site includes a timeline of scheduled events, the particulars about the spacecraft and its instruments, and a wide range of multimedia files and images. In keeping with NASA's high video standards, there are a number of rather remarkable short films here, including one that shows the LRO orbiting the moon.

249

An Orbit Plan toward AKATSUKI Venus Reencounter and Orbit Injection  

NASA Technical Reports Server (NTRS)

On December 7, 2010, AKATSUKI, the Japanese Venus explorer reached its destination and tried to inject itself into Venus orbit. However, due to a malfunction of the propulsion system, the maneuver was interrupted and AKATSUKI again escaped out from the Venus into an interplanetary orbit. Telemetry data from AKATSUKI suggests the possibility to perform orbit maneuvers to reencounter the Venus and retry Venus orbit injection. Reported in this paper is an orbit plan investigated under this situation. The latest results reflecting the maneuvers conducted in the autumn 2011 is introduced as well.

Kawakatsu, Yasuhiro; Campagnola, Stefano; Hirose, Chikako; Ishii, Nobuaki

2012-01-01

250

Examination of trajectories between low planetary orbits and circulation orbits  

NASA Astrophysics Data System (ADS)

Circulating orbits have been investigated to provide regular periodic transfers between the Earth and Mars. The circulating orbits pass close enough to each planet to be considered hyperbolic in planetocentric frame. The large spacecraft (CASTLE) in the circulating orbit is resupplied by a smaller 'Taxi' spacecraft leaving a low planetary orbit. The Taxi follows an optimal three-impulse patched-conic trajectory to travel from its spaceport to the large spacecraft following a hyperbolic fly-by. Examining the parameters of the situation produces a Delta V profile for each planetary fly-by of the circulating orbit.

Knoedler, Andrew J.

251

Orbiter KU-band transmitter  

NASA Technical Reports Server (NTRS)

The design, build, and test of an engineering breadboard Ku band quadraphase shift keyed and wideband frequency modulated transmitter are described. This orbiter Ku band transmitter drawer is to simulate the orbiter transmitter and meet the functional requirements of the orbiter communication link.

Halterman, R.

1976-01-01

252

Orbiter OMS and RCS technology  

NASA Technical Reports Server (NTRS)

Orbiter Orbital Maneuver Subsystem (OMS) and Reaction Control Subsystem (RCS) tankage has proved to be highly successful in shuttle flights on-orbit propellant transfer tests were done. Tank qualification tests along with flight demonstrations were carried out future uses of storable propellants are cited.

Boudreaux, R. A.

1982-01-01

253

Small Mercury Relativity Orbiter  

NASA Technical Reports Server (NTRS)

The accuracy of solar system tests of gravitational theory could be very much improved by range and Doppler measurements to a Small Mercury Relativity Orbiter. A nearly circular orbit at roughly 2400 km altitude is assumed in order to minimize problems with orbit determination and thermal radiation from the surface. The spacecraft is spin-stabilized and has a 30 cm diameter de-spun antenna. With K-band and X-band ranging systems using a 50 MHz offset sidetone at K-band, a range accuracy of 3 cm appears to be realistically achievable. The estimated spacecraft mass is 50 kg. A consider-covariance analysis was performed to determine how well the Earth-Mercury distance as a function of time could be determined with such a Relativity Orbiter. The minimum data set is assumed to be 40 independent 8-hour arcs of tracking data at selected times during a two year period. The gravity field of Mercury up through degree and order 10 is solved for, along with the initial conditions for each arc and the Earth-Mercury distance at the center of each arc. The considered parameters include the gravity field parameters of degree 11 and 12 plus the tracking station coordinates, the tropospheric delay, and two parameters in a crude radiation pressure model. The conclusion is that the Earth-Mercury distance can be determined to 6 cm accuracy or better. From a modified worst-case analysis, this would lead to roughly 2 orders of magnitude improvement in the knowledge of the precession of perihelion, the relativistic time delay, and the possible change in the gravitational constant with time.

Bender, Peter L.; Vincent, Mark A.

1989-01-01

254

Orbital Debris Modeling  

NASA Technical Reports Server (NTRS)

Presentation outlne: (1) The NASA Orbital Debris (OD) Engineering Model -- A mathematical model capable of predicting OD impact risks for the ISS and other critical space assets (2) The NASA OD Evolutionary Model -- A physical model capable of predicting future debris environment based on user-specified scenarios (3) The NASA Standard Satellite Breakup Model -- A model describing the outcome of a satellite breakup (explosion or collision)

Liou, J. C.

2012-01-01

255

Backtrack Orbit Search Algorithm  

Microsoft Academic Search

A Mathematical Solution to a Mathematical Problem. With the dramatic increase in satellite-born sensor resolution traditional methods of spatially searching for orbital data have become inadequate. As data volumes increase end-users of the data have become increasingly intolerant of false positives. And, as computing power rapidly increases end-users have come to expect equally rapid search speeds. Meanwhile data archives have

K. Knowles; R. Swick

2002-01-01

256

Spectrophotovoltaic orbital power generation  

NASA Technical Reports Server (NTRS)

The feasibilty of a spectrophotovoltaic orbital power generation system that optically concentrates solar energy is demonstrated. A dichroic beam-splitting mirror is used to divide the solar spectrum into two wavebands. Absorption of these wavebands by GaAs and Si solar cell arrays with matched energy bandgaps increases the cell efficiency while decreasing the amount of heat that must be rejected. The projected cost per peak watt if this system is $2.50/W sub p.

Onffroy, J. R.

1980-01-01

257

[Echinococcosis of the orbit].  

PubMed

A 5 year old girl with an echinococcuscyst in the right orbit is reported. The final diagnosis was made by removal of the cyst. A second cyst was found in the liver. The epidemiology, clinical and diagnostic problems of echinococcosis are reviewed. Radical surgery is still the only reliable treatment. For inoperable cases chemotherapy with Mebendazol seems promising. Many problems of chemotherapy remain to be solved and Mebendazol therapy is still in an experimental stage. PMID:4077595

Staindl, O; Krenkel, C

1985-09-01

258

Orbital spacecraft consumables resupply  

NASA Technical Reports Server (NTRS)

The capability to replenish spacecraft, satellites, and laboratories on-orbit with consumable fluids provides significant increases in their cost and operational effectiveness. Tanker systems to perform on-orbit fluid resupply must be flexible enough to operate from the Space Transportation System (STS), Space Station, or the Orbital Maneuvering Vehicle (OMV), and to accommodate launch from both the Shuttle and Expendable Launch Vehicles (ELV's). Resupply systems for storable monopropellant hydrazine and bipropellants, and water have been developed. These studies have concluded that designing tankers capable of launch on both the Shuttle and ELV's was feasible and desirable. Design modifications and interfaces for an ELV launch of the tanker systems were identified. Additionally, it was determined that modularization of the tanker subsystems was necessary to provide the most versatile tanker and most efficient approach for use at the Space Station. The need to develop an automatic umbilical mating mechanism, capable of performing both docking and coupler mating functions was identified. Preliminary requirements for such a mechanism were defined. The study resulted in a modular tanker capable of resupplying monopropellants, bipropellants, and water with a single design.

Dominick, Sam M.; Eberhardt, Ralph N.; Tracey, Thomas R.

1988-01-01

259

Orbiter Autoland reliability analysis  

NASA Technical Reports Server (NTRS)

The Space Shuttle Orbiter is the only space reentry vehicle in which the crew is seated upright. This position presents some physiological effects requiring countermeasures to prevent a crewmember from becoming incapacitated. This also introduces a potential need for automated vehicle landing capability. Autoland is a primary procedure that was identified as a requirement for landing following and extended duration orbiter mission. This report documents the results of the reliability analysis performed on the hardware required for an automated landing. A reliability block diagram was used to evaluate system reliability. The analysis considers the manual and automated landing modes currently available on the Orbiter. (Autoland is presently a backup system only.) Results of this study indicate a +/- 36 percent probability of successfully extending a nominal mission to 30 days. Enough variations were evaluated to verify that the reliability could be altered with missions planning and procedures. If the crew is modeled as being fully capable after 30 days, the probability of a successful manual landing is comparable to that of Autoland because much of the hardware is used for both manual and automated landing modes. The analysis indicates that the reliability for the manual mode is limited by the hardware and depends greatly on crew capability. Crew capability for a successful landing after 30 days has not been determined yet.

Welch, D. Phillip

1993-01-01

260

Global Orbit Feedback in RHIC  

SciTech Connect

For improved reproducibility of good operating conditions and ramp commissioning efficiency, new dual-plane slow orbit feedback during the energy ramp was implemented during run-10 in the Relativistic Heavy Ion Collider (RHIC). The orbit feedback is based on steering the measured orbit, after subtraction of the dispersive component, to either a design orbit or to a previously saved reference orbit. Using multiple correctors and beam position monitors, an SVD-based algorithm is used for determination of the applied corrections. The online model is used as a basis for matrix computations. In this report we describe the feedback design, review the changes made to realize its implementation, and assess system performance.

Minty, M.; Hulsart, R.; Marusic, A.; Michnoff, R.; Ptitsyn, V.; Robert-Demolaize, G.; Satogata, T.

2010-05-23

261

Visible Nulling Coronagraph Testbed Results  

NASA Technical Reports Server (NTRS)

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a NASA Astrophysics Strategic Mission Concept study and a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC would provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 5-year mission lifetime. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables starlight suppression in broadband light from 480-960 nm. To demonstrate the VNC approach and advance it's technology readiness we have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed.

Lyon, Richard G.; Clampin, Mark; Melnick, Gary; Tolls, Volker; Woodruff, Robert; Vasudevan, Gopal; Rizzo, Maxime; Thompson, Patrick

2009-01-01

262

Extrasolar Planetary Imaging Coronagraph: Visible Nulling Coronagraph Testbed Results  

NASA Technical Reports Server (NTRS)

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 3-year mission lifetime ( 5 year goal) and will revisit planets at least three times at intervals of 9 months. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables high order starlight suppression in broadband light. To demonstrate the VNC approach and advance it's technology readiness the NASA Goddard Space Flight Center and Lockheed-Martin have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed,

Lyon, Richard G.

2008-01-01

263

Lunar Prospector Orbit Determination Results  

NASA Technical Reports Server (NTRS)

The orbit support for Lunar Prospector (LP) consists of three main areas: (1) cislunar orbit determination, (2) rapid maneuver assessment using Doppler residuals, and (3) routine mapping orbit determination. The cislunar phase consisted of two trajectory correction maneuvers during the translunar cruise followed by three lunar orbit insertion burns. This paper will detail the cislunar orbit determination accuracy and the real-time assessment of the cislunar trajectory correction and lunar orbit insertion maneuvers. The non-spherical gravity model of the Moon is the primary influence on the mapping orbit determination accuracy. During the first two months of the mission, the GLGM-2 lunar potential model was used. After one month in the mapping orbit, a new potential model was developed that incorporated LP Doppler data. This paper will compare and contrast the mapping orbit determination accuracy using these two models. LP orbit support also includes a new enhancement - a web page to disseminate all definitive and predictive trajectory and mission planning information. The web site provides definitive mapping orbit ephemerides including moon latitude and longitude, and four week predictive products including: ephemeris, moon latitude/longitude, earth shadow, moon shadow, and ground station view periods. This paper will discuss the specifics of this web site.

Beckman, Mark; Concha, Marco

1998-01-01

264

Orbital Debris: A Policy Perspective  

NASA Technical Reports Server (NTRS)

A viewgraph presentation describing orbital debris from a policy perspective is shown. The contents include: 1) Voyage through near-Earth Space-animation; 2) What is Orbital Debris?; 3) Orbital Debris Detectors and Damage Potential; 4) Hubble Space Telescope; 5) Mir Space Station Solar Array; 6) International Space Station; 7) Space Shuttle; 8) Satellite Explosions; 9) Satellite Collisions; 10) NASA Orbital Debris Mitigation Guidelines; 11) International Space Station Jettison Policy; 12) Controlled/Uncontrolled Satellite Reentries; 13) Return of Space Objects; 14) Orbital Debris and U.S. National Space Policy; 15) U.S Government Policy Strategy; 16) Bankruptcy of the Iridium Satellite System; 17) Inter-Agency Space Debris Coordination Committee (IADC); 18) Orbital Debris at the United Nations; 19) Chinese Anti-satellite System; 20) Future Evolution of Satellite Population; and 21) Challenge of Orbital Debris

Johnson, Nicholas L.

2007-01-01

265

Mars orbits with daily repeating ground traces  

NASA Technical Reports Server (NTRS)

This paper derives orbits at Mars with ground traces that repeat at the same times every solar day (sol). A relay orbiter in such an orbit would pass over insitu probes at the same times every sol, ensuring consistent coverage and simplifying mission design and operations. 42 orbits in five classes are characteried: 14 cicular equatorial prograde orbits; 14 circular equatorial retrograde orbits; 11 circular sun synchrounous orbits; 2 eccentroc equatorial orbits; 1 eccentric critcally inclined orbit. the paper reports on the performance of a relay orbiter in some of the orbits.

Noreen, Gary K.; Kerridge, Stuart; Diehl, Roger; neelon, Joseph; Ely, Todd; Turner, Andrew

2003-01-01

266

Lunar Exploration Orbiter (LEO)  

NASA Astrophysics Data System (ADS)

The Moon is an integral part of the Earth-Moon system, it is a witness to more than 4.5 b. y. of solar system history, and it is the only planetary body except Earth for which we have samples from known locations. The Moon is our closest companion and can easily be reached from Earth at any time, even with a relatively modest financial budget. Consequently, the Moon was the first logical step in the exploration of our solar system before we pursued more distant targets such as Mars and beyond. The vast amount of knowledge gained from the Apollo and other lunar missions of the late 1960's and early 1970's demonstrates how valuable the Moon is for the understanding of our planetary system. Even today, the Moon remains an extremely interesting target scientifically and technologically, as ever since, new data have helped to address some of our questions about the Earth-Moon system, many questions remained. Therefore, returning to the Moon is the critical stepping-stone to further exploring our immediate planetary neighborhood. In this concept study, we present scientific and technological arguments for a national German lunar mission, the Lunar Explorations Orbiter (LEO). Numerous space-faring nations have realized and identified the unique opportunities related to lunar exploration and have planned missions to the Moon within the next few years. Among these missions, LEO will be unique, because it will globally explore the Moon in unprecedented spatial and spectral resolution. LEO will significantly improve our understanding of the lunar surface composition, surface ages, mineralogy, physical properties, interior, thermal history, gravity field, regolith structure, and magnetic field. The Lunar Explorations Orbiter will carry an entire suite of innovative, complementary technologies, including high-resolution camera systems, several spectrometers that cover previously unexplored parts of the electromagnetic spectrum over a broad range of wavelengths, microwave and radar experiments, a very sensitive magnetometer and gradiometer, a subsatellite, and a state-of-the-art optical communication system. The Lunar Explorations Orbiter concept is technologically challenging but feasible, and will gather unique, integrated, interdisciplinary data sets that are of high scientific interest and will provide an unprecedented new context for all other international lunar missions. In fact, the Lunar Explorations Orbiter will further establish Germany as a leader among space-faring nations and will demonstrate expertise and technological know-how, which is "Made in Germany". With its high visibility, LEO will foster the growing acceptance of space exploration in Germany and will capture the imagination of the general public.

Jaumann, R.; Spohn, T.; Hiesinger, H.; Jessberger, E. K.; Neukum, G.; Oberst, J.; Helbert, J.; Christensen, U.; Keller, H. U.; Mall, U.; Böhnhardt, H.; Hartogh, P.; Glassmeier, K.-H.; Auster, H.-U.; Moreira, A.; Werner, M.; Pätzold, M.; Palme, H.; Wimmer-Schweingruber, R.; Mandea, M.; Lesur, V.; Häusler, B.; Hördt, A.; Eichentopf, K.; Hauber, E.; Hoffmann, H.; Köhler, U.; Kührt, E.; Michaelis, H.; Pauer, M.; Sohl, F.; Denk, T.; van Gasselt, S.

2007-08-01

267

The Earth's Orbit  

NSDL National Science Digital Library

These eleven activities relate to the results of the motion and position of the Earth in its orbit, investigating both the causes and the effects of changing seasons. It starts simply by trying to quantify the observation that it is colder in the winter and ends by measuring the tilt of the Earth. This is chapter two of the online book Eyes on the Sky, Feet on the Ground, containing explorations into astronomy as a classroom tool for learning how to theorize, experiment, and analyze data. The activities are fully illustrated and contain detailed, step-by-step instructions as well as suggested discussion topics.

2007-12-12

268

Weather Satellite and Orbits  

NSDL National Science Digital Library

In this interactive, online module, students learn about satellite orbits (geostationary and polar), remote-sensing satellite instruments (radiometers and sounders), satellite images, and the math and physics behind satellite technology. The module is part of an online course for grades 7-12 in satellite meteorology, which includes 10 interactive modules. The site also includes lesson plans developed by teachers and links to related resources. Each module is designed to serve as a stand-alone lesson, however, a sequential approach is recommended. Designed to challenge students through the end of 12th grade, middle school teachers and students may choose to skim or skip a few sections.

269

[Endoscopic approaches to the orbit].  

PubMed

During the last decade, the use of endoscopic endonasal approaches to the pituitary has increased considerably. The endoscopic endonasal and transantral approaches offer a minimally invasive alternative to the classic transcranial or transconjunctival approaches to the medial aspect of the orbit. The medial wall of the orbit, the orbital apex, and the optic canal can be exposed through a middle meatal antrostomy, an anterior and posterior ethmoidectomy, and a sphenoidotomy. The inferomedial wall of the orbit can be also perfectly visualized through a sublabial antrostomy or an inferior meatal antrostomy. Several reports have described the use of an endoscopic approach for the resection or the biopsy of lesions located on the medial extraconal aspect of the orbit and orbital apex. However, the resection of intraconal lesions is still limited by inadequate instrumentation. Other indications for the endoscopic approach to the orbit are the decompression of the orbit for Graves' ophthalmopathy and traumatic optic neuropathy. However, the optimal management of traumatic optic neuropathy remains very controversial. Endoscopic endonasal decompression of the optic nerve in case of tumor compression could be a more valid indication in combination with radiation therapy. Finally, the endoscopic transantral treatment of blowout fracture of the floor of the orbit is an interesting option that avoids the eyelid or conjunctive incision of traditional approaches. The collaboration between the neurosurgeon and the ENT surgeon is mandatory and reduces the morbidity of the approach. Progress in instrumentation and optical devices will certainly make this approach promising for intraconal tumor of the orbit. PMID:20347457

Cebula, H; Lahlou, A; De Battista, J C; Debry, C; Froelich, S

2010-01-01

270

Finite thrust orbital transfers  

NASA Astrophysics Data System (ADS)

The finite thrust optimal transfer in the presence of the Earth's shadow and oblate planet perturbations is a problem of strong interest in modern telecommunication satellite design with plasmic propulsion. The Maximum Principle cannot be used in its standard form to deal with the Earth's shadow. In this paper, using a regularization of the Hamiltonian which expands the Maximum Principle application domain, we provide for the first time, the necessary conditions in a very general context for the finite thrust optimal transfer with limited power around an oblate planet. The costate in such problems is generally discontinuous. To obtain fast numerical solutions, the averaging of the Hamiltonian is introduced. Two classes of boundary conditions are analyzed and numerically solved: the minimum time and the minimum fuel at a fixed time. These two problems are the basic tools for designing the orbit raising of a satellite after the launcher injection into its separation orbit. Numerical solutions have been calculated for the more important applications of LEO to GEO/MEO missions and the results have been reported and discussed.

Mazzini, Leonardo

2014-07-01

271

Orbital construction demonstration study  

NASA Technical Reports Server (NTRS)

A conceptual design and program plan for an Orbital Construction Demonstration Article (OCDA) was developed that can be used for evaluating and establishing practical large structural assembly operations. A flight plan for initial placement and continued utility is presented as a basic for an entirely new shuttle payload line-item having great future potential benefit for space applications. The OCDA is a three-axis stabilized platform in low-earth orbit with many structural nodals for mounting large construction and fabrication equipments. This equipment would be used to explore methods for constructing the large structures for future missions. The OCDA would be supported at regular intervals by the shuttle. Construction experiments and consumables resupply are performed during shuttle visit periods. A 250 kw solar array provides sufficient power to support the shuttle while attached to the OCDA and to run construction experiments at the same time. Wide band communications with a Telemetry and Data Relay Satellite compatible high gain antenna can be used between shuttle revisits to perform remote controlled, TV assisted construction experiments.

1976-01-01

272

General view of the Orbiter Discovery in the Orbiter Processing ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

General view of the Orbiter Discovery in the Orbiter Processing Facility at Kennedy Space Center showing the payload bay doors open exposing the heat-dissipating radiator panels located on the inside of the payload bay doors. Also in the view is the boom portion of the boom sensor system deployed as part of the return to flight procedures after STS-107 to inspect the orbiter's thermal protection system. The Remote Manipulator System, the "Canadarm", and the airlock are seen in the background of the image. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

273

Orbital State Uncertainty Realism  

NASA Astrophysics Data System (ADS)

Fundamental to the success of the space situational awareness (SSA) mission is the rigorous inclusion of uncertainty in the space surveillance network. The *proper characterization of uncertainty* in the orbital state of a space object is a common requirement to many SSA functions including tracking and data association, resolution of uncorrelated tracks (UCTs), conjunction analysis and probability of collision, sensor resource management, and anomaly detection. While tracking environments, such as air and missile defense, make extensive use of Gaussian and local linearity assumptions within algorithms for uncertainty management, space surveillance is inherently different due to long time gaps between updates, high misdetection rates, nonlinear and non-conservative dynamics, and non-Gaussian phenomena. The latter implies that "covariance realism" is not always sufficient. SSA also requires "uncertainty realism"; the proper characterization of both the state and covariance and all non-zero higher-order cumulants. In other words, a proper characterization of a space object's full state *probability density function (PDF)* is required. In order to provide a more statistically rigorous treatment of uncertainty in the space surveillance tracking environment and to better support the aforementioned SSA functions, a new class of multivariate PDFs are formulated which more accurately characterize the uncertainty of a space object's state or orbit. The new distribution contains a parameter set controlling the higher-order cumulants which gives the level sets a distinctive "banana" or "boomerang" shape and degenerates to a Gaussian in a suitable limit. Using the new class of PDFs within the general Bayesian nonlinear filter, the resulting filter prediction step (i.e., uncertainty propagation) is shown to have the *same computational cost as the traditional unscented Kalman filter* with the former able to maintain a proper characterization of the uncertainty for up to *ten times as long* as the latter. The filter correction step also furnishes a statistically rigorous *prediction error* which appears in the likelihood ratios for scoring the association of one report or observation to another. Thus, the new filter can be used to support multi-target tracking within a general multiple hypothesis tracking framework. Additionally, the new distribution admits a distance metric which extends the classical Mahalanobis distance (chi^2 statistic). This metric provides a test for statistical significance and facilitates single-frame data association methods with the potential to easily extend the covariance-based track association algorithm of Hill, Sabol, and Alfriend. The filtering, data fusion, and association methods using the new class of orbital state PDFs are shown to be mathematically tractable and operationally viable.

Horwood, J.; Poore, A. B.

2012-09-01

274

Adaptive interplanetary orbit determination  

NASA Astrophysics Data System (ADS)

This work documents the development of a real-time interplanetary orbit determination monitoring algorithm for detecting and identifying changes in the spacecraft dynamic and measurement environments. The algorithm may either be utilized in a stand-alone fashion as a spacecraft monitor and hypothesis tester by navigators or may serve as a component in an autonomous adaptive orbit determination architecture. In either application, the monitoring algorithm serves to identify the orbit determination filter parameters to be modified by an offline process to restore the operational model accuracy when the spacecraft environment changes unexpectedly. The monitoring algorithm utilizes a hierarchical mixture-of-experts to regulate a multilevel bank organization of extended Kalman filters. Banks of filters operate on the hierarchy top-level and are composed of filters with configurations representative of a specific environment change called a macromode. Fine differences, or micromodes, within the macromodes are represented by individual filter configurations. Regulation is provided by two levels of single-layer neural networks called gating networks. A single top-level gating network regulates the weighting among macromodes and each bank uses a gating network to regulate member filters internally. Experiments are conducted on the Mars Pathfinder cruise trajectory environment using range and Doppler data from the Deep Space Network. The experiments investigate the ability of the hierarchical mixture-of-experts to identify three environment macromodes: (1) unmodeled impulsive maneuvers, (2) changes in the solar radiation pressure dynamics, and (3) changes in the measurement noise strength. Two methods of initializing the gating networks are examined in each experiment. One method gives the neurons associated with all filters equivalent synaptic weight. The other method places greater weight on the operational filter initially believed to model the spacecraft environment. The results will show that the equal synaptic weight initialization method is superior to the one favoring the operational filter and that processing range and Doppler data together is superior to processing Doppler data alone. When processing range and Doppler with an equally initialized hierarchy, all three macromodes are definitively identified by the top-level gating network weights. Additionally, in the case of multiple successive macromode changes, the hierarchy is generally able to recover from one macromode and identify a change to another macromode.

Crain, Timothy Price

275

'Columbia Hills' from Orbit  

NASA Technical Reports Server (NTRS)

This view of the 'Columbia Hills' in Gusev Crater was made by draping an image from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter (image E0300012 from that camera) over a digital elevation model that was derived from two Mars Orbiter Camera images (E0300012 and R0200357).

This unique view is helpful to the rover team members as they plan the journey of NASA's Mars Exploration Rover Spirit to the base of the Columbia Hills and beyond. Spirit successfully completed a three-month primary mission, and so far remains healthy in an extended mission of bonus exploration. As of sol 135 (on May 21, 2004), Spirit sits approximately 680 meters (0.4 miles) away from its first target at the western base of the hills, a spot informally called 'West Spur.' The team estimates that Spirit will reach West Spur by sol 146 (June 1, 2004). Spirit will most likely remain there for about a week to study the outcrops and rocks associated with this location.

When done there, Spirit will head approximately 620 meters (0.38 miles) to a higher-elevation location informally called 'Lookout Point.' Spirit might reach Lookout Point by around sol 165 (June 20, 2004). On the way, the rover will pass by and study ripple-shaped wind deposits that may reveal more information about wind processes on Mars.

Lookout Point will provide a great vantage point for scientists to remotely study the inner basin area of the Columbia Hills. This basin contains a broad range of interesting geological targets including the informally named 'Home Plate' and other possible layered outcrops. These features suggest that the hills contain rock layers. Spirit might investigate the layers to determine whether they are water-deposited sedimentary rock.

Once at Lookout Point, Spirit will acquire 360-degree panoramic images of the entire area to help define the rover's next steps. Assuming the rover stays healthy, Spirit will eventually drive down into the basin to get an up-close look at interesting features there.

2004-01-01

276

OSO-6 Orbiting Solar Observatory  

NASA Technical Reports Server (NTRS)

The description, development history, test history, and orbital performance analysis of the OSO-6 Orbiting Solar Observatory are presented. The OSO-6 Orbiting Solar Observatory was the sixth flight model of a series of scientific spacecraft designed to provide a stable platform for experiments engaged in the collection of solar and celestial radiation data. The design objective was 180 days of orbital operation. The OSO-6 has telemetered an enormous amount of very useful experiment and housekeeping data to GSFC ground stations. Observatory operation during the two-year reporting period was very successful except for some experiment instrument problems.

1972-01-01

277

Aerobraked orbital transfer vehicle definition  

NASA Astrophysics Data System (ADS)

A new technique has been developed to enhance the use of upper atmosphere aerobraking for increased performance from orbital transfer vehicles. This technique utilizes a pressure supported drag brake and the orbital transfer vehicle main engine to modulate aerodynamic drag and also to alleviate the aerodynamic heating during a grazing pass through the atmosphere. Performance analyses of vehicles utilizing all-propulsive or aerobraking during round trip missions from low earth orbit (LEO) to geo-synchronous earth orbit (GEO) and back shows that aerobraking allows a given vehicle to deliver approximately twice as much payload to GEO and return. Aerobraking also provides more than twice the round trip payload.

Andrews, D. G.; Bloetscher, F.

1981-01-01

278

Orbital molecules in electronic materials  

NASA Astrophysics Data System (ADS)

Orbital molecules are made up of coupled orbital states on several metal ions within an orbitally ordered (and sometimes also charge-ordered) solid such as a transition metal oxide. Spin-singlet dimers are known in many materials, but recent discoveries of more exotic species such as 18-electron heptamers in AlV2O4 and magnetic 3-atom trimerons in magnetite (Fe3O4) have shown that orbital molecules constitute a general new class of quantum electronic states in solids.

Attfield, J. Paul

2015-04-01

279

Orbiter Servicer Rendezvous Simulation (ORSIM)  

NASA Astrophysics Data System (ADS)

Orbiter Servicer Rendezvous Simulation (ORSIM) is an automated tool that simulates sequential transfer maneuvers of an orbital maneuvering vehicle (OMV) transporting orbital replaceable units from a space-based depot, or logistics platform, to higher altitude SDI sdatellites. ORSIM calculates OMV energy expenditures (velocity changes) and event histories for various combinations of user-selected orbital transfer maneuvers. Additionally, ORSIM determines the optimal configuration/quantities of logistics platforms and OMVs which conform to the dynamics of differential nodal precession, given user-prescribed values of the scheduled maintenance cycle and required servicing times. ORSIM is coded in FORTRAN-77 and is resident on an IBM PC/AT.

Amato, Amiel; Hoffman, Mickie D.

280

Periodic orbits in warped disk  

E-print Network

It is often assumed that a warped galaxy can be modeled by a set of rings. This paper verifies numerically the validity of this assumption by the study of periodic orbits populating a heavy self-gravitating warped disk. The phase space structure of a warped model reveals that the circular periodic orbits of a flat disk are transformed in quasi annular periodic orbits which conserve their stability. This lets us also explore the problem of the persistence of a large outer warp. In particular, the consistency of its orbits with the density distribution is checked as a function of the pattern speed.

Y. Revaz; D. Pfenniger

2001-05-10

281

The Košice meteorite fall: Atmospheric trajectory, fragmentation, and orbit  

NASA Astrophysics Data System (ADS)

The Košice meteorite fall occurred in eastern Slovakia on February 28, 2010, 22:25 UT. The very bright bolide was imaged by three security video cameras from Hungary. Detailed bolide light curves were obtained through clouds by radiometers on seven cameras of the European Fireball Network. Records of sonic waves were found on six seismic and four infrasonic stations. An atmospheric dust cloud was observed the next morning before sunrise. After careful calibration, the video records were used to compute the bolide trajectory and velocity. The meteoroid, of estimated mass of 3500 kg, entered the atmosphere with a velocity of 15 km s-1 on a trajectory with a slope of 60° to the horizontal. The largest fragment ceased to be visible at a height of 17 km, where it was decelerated to 4.5 km s-1. A maximum brightness of absolute stellar magnitude about -18 was reached at a height of 36 km. We developed a detailed model of meteoroid atmospheric fragmentation to fit the observed light curve and deceleration. We found that Košice was a weak meteoroid, which started to fragment under the dynamic pressure of only 0.1 MPa and fragmented heavily under 1 MPa. In total, 78 meteorites were recovered in the predicted fall area during official searches. Other meteorites were found by private collectors. Known meteorite masses ranged from 0.56 g to 2.37 kg. The meteorites were classified as ordinary chondrites of type H5 and shock stage S3. The heliocentric orbit had a relatively large semimajor axis of 2.7 AU and aphelion distance of 4.5 ± 0.5 AU. Backward numerical integration of the preimpact orbit indicates possible large variations of the orbital elements in the past due to resonances with Jupiter.

Borovi?Ka, Ji?í; Tóth, Juraj; Igaz, Antal; Spurný, Pavel; Kalenda, Pavel; Haloda, Jakub; Svoreå, Ján; Kornoš, Leonard; Silber, Elizabeth; Brown, Peter; HusáRik, Marek

2013-10-01

282

Orbiting Carbon Observatory  

NASA Technical Reports Server (NTRS)

Human impact on the environment has produced measurable changes in the geological record since the late 1700s. Anthropogenic emissions of CO2 today may cause the global climate to depart for its natural behavior for many millenia. CO2 is the primary anthropogenic driver of climate change. The Orbiting Carbon Observatory goals are to help collect measurements of atmospheric CO2, answering questions such as why the atmospheric CO2 buildup varies annually, the roles of the oceans and land ecosystems in absorbing CO2, the roles of North American and Eurasian sinks and how these carbon sinks respond to climate change. The present carbon cycle, CO2 variability, and climate uncertainties due atmospheric CO2 uncertainties are highlighted in this presentation.

Miller, Charles E.

2005-01-01

283

TOPEX orbital radiation study  

NASA Technical Reports Server (NTRS)

The space radiation environment of the TOPEX spacecraft is investigated. A single trajectory was considered. The external (surface incident) charged particle radiation, predicted for the satellite, is determined by orbital flux integration for the specified trajectory. The latest standard models of the environment are used in the calculations. The evaluation is performed for solar maximum conditions. The spacecraft exposure to cosmic rays of galactic origin is evaluated over its flight path through the magnetosphere in terms of geomagnetic shielding effects, both for surface incident heavy ions and for particles emerging behind different material thickness. Limited shielding and dose evaluations are performed for simple infinite slab and spherical geometries. Results, given in graphical and tabular form, are analyzed, explained, and discussed. Conclusions are presented and commented on.

Stassinopoulos, E. G.; Barth, J. M.

1984-01-01

284

Exploratory orbit analysis  

SciTech Connect

Unlike the other documents in these proceedings, this paper is neither a scientific nor a technical report. It is, rather, a short personal essay which attempts to describe an Exploratory Orbit Analysis (EOA) environment. Analyzing the behavior of a four or six dimensional nonlinear dynamical system is at least as difficult as analyzing events in high-energy collisions; the consequences of doing it badly, or slowly, would be at least as devastating; and yet the level of effort and expenditure invested in the latter, the very attention paid to it by physicists at large, must be two orders of magnitude greater than that given to the former. It is difficult to choose the model which best explains the behavior of a physical device if one does not first understand the behavior of the available models. The time is ripe for the development of a functioning EOA environment, which I will try to describe in this paper to help us achieve this goal.

Michelotti, L.

1989-03-01

285

Orbital science's 'Bermuda Triangle'  

NASA Astrophysics Data System (ADS)

The effects of a part of the inner Van Allen belt lying closest to the earth, known as the South Atlantic Anomaly (SAA) upon spacecraft including the Hubble Space Telescope (HST), are discussed. The area consists of positively charged ions and electrons from the Van Allen Belt which become trapped in the earth's dipole field. Contor maps representing the number of protons per square centimeter per second having energies greater than 10 million electron volts are presented. It is noted that the HST orbit causes it to spend about 15 percent of its time in the SAA, but that, unlike the experience with earlier spacecraft, the satellite's skin, internal structure, and normal electronic's packaging provides sufficient protection against eletrons, although some higher energy protons still get through. Various charged particle effects which can arise within scientific instruments including fluorescence, Cerenkov radiation, and induced radioactivity are described.

Sherrill, Thomas J.

1991-02-01

286

Orbit Determination Toolbox  

NASA Technical Reports Server (NTRS)

The Orbit Determination Toolbox is an orbit determination (OD) analysis tool based on MATLAB and Java that provides a flexible way to do early mission analysis. The toolbox is primarily intended for advanced mission analysis such as might be performed in concept exploration, proposal, early design phase, or rapid design center environments. The emphasis is on flexibility, but it has enough fidelity to produce credible results. Insight into all flight dynamics source code is provided. MATLAB is the primary user interface and is used for piecing together measurement and dynamic models. The Java Astrodynamics Toolbox is used as an engine for things that might be slow or inefficient in MATLAB, such as high-fidelity trajectory propagation, lunar and planetary ephemeris look-ups, precession, nutation, polar motion calculations, ephemeris file parsing, and the like. The primary analysis functions are sequential filter/smoother and batch least-squares commands that incorporate Monte-Carlo data simulation, linear covariance analysis, measurement processing, and plotting capabilities at the generic level. These functions have a user interface that is based on that of the MATLAB ODE suite. To perform a specific analysis, users write MATLAB functions that implement truth and design system models. The user provides his or her models as inputs to the filter commands. The software provides a capability to publish and subscribe to a software bus that is compliant with the NASA Goddard Mission Services Evolution Center (GMSEC) standards, to exchange data with other flight dynamics tools to simplify the flight dynamics design cycle. Using the publish and subscribe approach allows for analysts in a rapid design center environment to seamlessly incorporate changes in spacecraft and mission design into navigation analysis and vice versa.

Carpenter, James R.; Berry, Kevin; Gregpru. Late; Speckman, Keith; Hur-Diaz, Sun; Surka, Derek; Gaylor, Dave

2010-01-01

287

PyORBIT: A Python Shell For ORBIT  

SciTech Connect

ORBIT is code developed at SNS to simulate beam dynamics in accumulation rings and synchrotrons. The code is structured as a collection of external C++ modules for SuperCode, a high level interpreter shell developed at LLNL in the early 1990s. SuperCode is no longer actively supported and there has for some time been interest in replacing it by a modern scripting language, while preserving the feel of the original ORBIT program. In this paper, we describe a new version of ORBIT where the role of SuperCode is assumed by Python, a free, well-documented and widely supported object-oriented scripting language. We also compare PyORBIT to ORBIT from the standpoint of features, performance and future expandability.

Jean-Francois Ostiguy; Jeffrey Holmes

2003-07-01

288

Nongravitational motions of comets: component of the recoil force normal to orbital plane  

NASA Astrophysics Data System (ADS)

The significance and detectability of a normal component of the nongravitational acceleration that perturbs the motions of periodic comets are examined by comparing the total perturbation effect, calculated from the component's empirical term in the equations of motion integrated over the orbital period, with the cumulative perturbations of the longitude of the ascending node and the orbital inclination brought about by the momentum that is transferred to the nucleus due to water outgassing from discrete active regions. It is shown that the approximation of temporal variations in the recoil acceleration computed using the well-known g(r) law, which is symmetrical with respect to perihelion, implies that the cumulative nongravitational perturbations of the two orbital elements are accounted for in a fashion that is inconsistent with the perturbation theory. The net result is that, in general, the value of the Style II nongravitational parameter that is consistent with the cumulative effect on the inclination, iA3, differs from the parameter's expected value that describes the cumulative effect on the nodal line, ?A3. The parameter's distributions as functions of the spin vector and the direction of the ejecta's vector (described by the thrust angle) are represented graphically for several heliocentric orbits. Symmetries with respect to particular values of the argument of perihelion, the rotation constants, and the thrust angle that apply in the case of a baseline model (which involves assumptions of a single source and the absence of sublimation lags) are identified. The magnitudes of the parameter A3 derived from orbit- determination runs are found to be generally compatible with the presented interpretation in that they are not excessive, thus supporting the evidence presented in an earlier paper (Sekanina 1993) and based upon information on the transverse and radial components of the recoil force. The values of iA3 and ?A3 are shown to coincide for certain spin-axis orientations and it is only then that the parameter A3 should reliably be determined from an orbital solution that employs the standard g(r) law. One such scenario appears to be closely approximated by Periodic Comet Clark, for which the data available are shown to provide meaningful constraints on the bulk properties of its nucleus. A potential need for a revision of the non-gravitational terms in the equations of motion is suggested.

Sekanina, Z.

1993-09-01

289

Structure of the zodiacal emission by Spitzer archive data  

NASA Astrophysics Data System (ADS)

Dust in the interplanetary dust cloud not just reflects the sunlight (known as zodiacal light) but also has its own thermal emission. At the heliocentric distance of the Earth, the peak of this emission (with particle size ˜ 100 ? m) is close to 20 ? m. In this study, we used the data of four programs completed with the MIPS camera of the Spitzer Space Telescope at 24 ? m to probe the large-scale brightness distribution as well as the small-scale (sub-arcmin) structure of the zodiacal cloud. The four programs were: - The Production of Zodiacal Dust by Asteroids and Comets (ID: 2317) - High Latitude Dust Bands in the Main Asteroid Belt: Fingerprints of Recent Breakup Events (ID: 20539) - A New Source of Interplanetary Dust: Type II Dust Trails (ID: 30545) - First Look Survey - Ecliptic Plane Component (ID: 98) We take into account that, when the Spitzer Space Telescope carried out the measurements, it was orbiting the Sun at an Earth-trailing orbit and looking at different parts of the zodiacal cloud, in many cases looking through the same parts of the cloud from different locations. This gives us the chance to investigate the 3D distribution of zodiacal dust in addition to large- and small-scale structure of the cloud.

Verebelyi, E.; Kiss, C.; Balog, Z.; Stansberry, J.

2014-07-01

290

Lageos orbit and solar eclipses  

NASA Technical Reports Server (NTRS)

The objective was to assess the importance of solar eclipses on Lageos' orbit. Solar radiation pressure perturbs the orbit of the Lageos satellite. The GEODYN orbit determination computer program includes solar radiation pressure as one of the forces operating on the satellite as it integrates the orbit. GEODYN also takes into account the extinction of sunlight when Lageos moves into the Earth's shadow. The effect of solar eclipses on the semimajor axis of Lageos' orbit was computed analytically by assuming Lageos to be in a circular orbit, the Sun and the Moon to be in the plane of the orbit, and the Moon to be stationary in the sky in front of the Sun. Also, the magnitude of the radiation pressure is assumed to be linearly related to the angular separation of the Sun and Moon, and that Lageos is a perfect absorber of radiation. The computation indicates that an eclipse of the Sun by the Moon as seen by Lageos can affect the semimajor axis at the 1 centimeter (1 cm) level. Such a change is significant enough to include in GEODYN, in order to get an accurate orbit for Lageos.

Rubincam, D. P.

1984-01-01

291

Giant Orbitals Currents in Nanostructures  

NASA Astrophysics Data System (ADS)

The possibility and origin of giant orbital currents [1] in nanostructures is investigated by model calculations. We compare two models: (i) a model where electrons are confined to a ``racetrack'' around the dot and (ii) a tight-binding model where atomic spin-orbit coupling creates macroscopic currents at the periphery of the dots. The first model yields expressions very similar to Ref. 1, but the corresponding spin-orbit coupling [2] is negligibly small, because it strongly decreases with increasing orbital radius. Furthermore, the orbital moment rapidly collapses due to a redistribution of electron with wave vectors of opposite sense of rotation. In the second model, the relatively strong intra-atomic spin-orbit interaction yields orbital currents that add [3] between neighboring atoms and create a macroscopic current at the periphery of the dot. This current corresponds to a magnetic Berry phase and cannot dissipate, because the underlying atomic orbital moments are quantized. References: [1] A. Hernando, P. Crespo, and M. A. Garc'ia, Phys. Rev. Lett. 96, 057206 (2006). [2] R. Skomski, IEEE Trans. Magn. 32, 4794 (1996). [3] J. Zhang, R. Skomski, Y. F. Lu, and D. J. Sellmyer, Phys. Rev. B 75, 214417 (2007).

Skomski, Ralph; Sellmyer, D. J.

2010-03-01

292

The 2009 Mars Telecommunications Orbiter  

Microsoft Academic Search

The first spacecraft with a primary function of providing communication links while orbiting a foreign planet has begun development for a launch in 2009. NASA's Mars Telecommunications Orbiter would use three radio bands to magnify the benefits of other future Mars missions and enable some types of missions otherwise impractical. It would serve as the Mars hub for a growing

G. R. Wilson; R. Depaula; R. E. Diehl; C. D. Edwards; R. J. Fitzgerald; S. F. Franklin; R. G. Gibbs; S. A. Kerridge; T. A. Komarek; G. K. Noreen

2004-01-01

293

ORBIT CONTROL ADVANCES AT ELETTRA  

Microsoft Academic Search

Advances in orbit control and concepts of a new algorithm are described that allow the simult aneous minimisation of the global orbit and correction kicks in a syst ematic way especially for a non-optimised machine. Although the algorithm is not SVD dependent, using it with SVD renders flexibility and transparency ensuring thereafter optimised solutions that are intrinsic to SVD. The

E. Karantzoulis

2000-01-01

294

Endoscopic treatment of orbital tumors  

PubMed Central

Different orbital and transcranial approaches are performed in order to manage orbital tumors, depending on the location and size of the lesion within the orbit. These approaches provide a satisfactory view of the superior and lateral aspects of the orbit and the optic canal but involve risks associated with their invasiveness because they require significant displacement of orbital structures. In addition, external approaches to intraconal lesions may also require deinsertion of extraocular muscles, with subsequent impact on extraocular mobility. Recently, minimally invasive techniques have been proposed as valid alternative to external approaches for selected orbital lesions. Among them, transnasal endoscopic approaches, “pure” or combined with external approaches, have been reported, especially for intraconal lesions located inferiorly and medially to the optic nerve. The avoidance of muscle detachment and the shortness of the surgical intraorbital trajectory makes endoscopic approach less invasive, thus minimizing tissue damage. Endoscopic surgery decreases the recovery time and improves the cosmetic outcome not requiring skin incisions. The purpose of this study is to review and discuss the current surgical techniques for orbital tumors removal, focusing on endoscopic approaches to the orbit and outlining the key anatomic principles to follow for safe tumor resection. PMID:25789299

Signorelli, Francesco; Anile, Carmelo; Rigante, Mario; Paludetti, Gaetano; Pompucci, Angelo; Mangiola, Annunziato

2015-01-01

295

Orbital anatomy for the surgeon.  

PubMed

An anatomic description of the orbit and its contents and the eyelids directed toward surgeons is the focus of this article. The bone and soft tissue anatomic nuances for surgery are highlighted, including a section on osteology, muscles, and the orbital suspensory system. Innervation and vascular anatomy are also addressed. PMID:23107426

Turvey, Timothy A; Golden, Brent A

2012-11-01

296

Endoscopic treatment of orbital tumors.  

PubMed

Different orbital and transcranial approaches are performed in order to manage orbital tumors, depending on the location and size of the lesion within the orbit. These approaches provide a satisfactory view of the superior and lateral aspects of the orbit and the optic canal but involve risks associated with their invasiveness because they require significant displacement of orbital structures. In addition, external approaches to intraconal lesions may also require deinsertion of extraocular muscles, with subsequent impact on extraocular mobility. Recently, minimally invasive techniques have been proposed as valid alternative to external approaches for selected orbital lesions. Among them, transnasal endoscopic approaches, "pure" or combined with external approaches, have been reported, especially for intraconal lesions located inferiorly and medially to the optic nerve. The avoidance of muscle detachment and the shortness of the surgical intraorbital trajectory makes endoscopic approach less invasive, thus minimizing tissue damage. Endoscopic surgery decreases the recovery time and improves the cosmetic outcome not requiring skin incisions. The purpose of this study is to review and discuss the current surgical techniques for orbital tumors removal, focusing on endoscopic approaches to the orbit and outlining the key anatomic principles to follow for safe tumor resection. PMID:25789299

Signorelli, Francesco; Anile, Carmelo; Rigante, Mario; Paludetti, Gaetano; Pompucci, Angelo; Mangiola, Annunziato

2015-03-16

297

Floating orbital molecular dynamics simulations.  

PubMed

We introduce an alternative ab initio molecular dynamics simulation as a unification of Hartree-Fock molecular dynamics and the floating orbital approach. The general scheme of the floating orbital molecular dynamics method is presented. Moreover, a simple but sophisticated guess for the orbital centers is provided to reduce the number of electronic structure optimization steps at each molecular dynamics step. The conservation of total energy and angular momentum is investigated in order to validate the floating orbital molecular dynamics approach with and without application of the initial guess. Finally, a water monomer and a water dimer are simulated, and the influence of the orbital floating on certain properties like the dipole moment is investigated. PMID:24600690

Perlt, Eva; Brüssel, Marc; Kirchner, Barbara

2014-04-21

298

The 2009 Mars Telecommunications Orbiter  

NASA Astrophysics Data System (ADS)

The first spacecraft with a primary function of providing communication links while orbiting a foreign planet has begun development for a launch in 2009. NASA's Mars Telecommunications Orbiter would use three radio bands to magnify the benefits of other future Mars missions and enable some types of missions otherwise impractical. It would serve as the Mars hub for a growing interplanetary Internet. And it would pioneer the use of planet-to-planet laser communications to demonstrate the possibility for even great networking capabilities in the future. During its nearly 10-year mission in orbit, Mars Telecommunications Orbiter would aid navigation of arriving spacecraft to their martian landing sites and monitor critical events during landings and orbit insertions. In addition, it would enable data-transmission volumes great enough to bring a virtual Mars presence to the public through a range of Internet and video features.

Wilson, G. R.; Depaula, R.; Diehl, R. E.; Edwards, C. D.; Fitzgerald, R. J.; Franklin, S. F.; Gibbs, R. G.; Kerridge, S. A.; Komarek, T. A.; Noreen, G. K.

299

Low Earth Orbiter: Terminal  

NASA Technical Reports Server (NTRS)

In response to the current government budgetary environment that requires the National Aeronautics and Space Administration (NASA) to do more with less, NASA/Goddard Space Flight Center's Wallops Flight Facility has developed and implemented a class of ground stations known as a Low Earth Orbiter-Terminal (LEO-T). This development thus provides a low-cost autonomous ground tracking service for NASA's customers. More importantly, this accomplishment provides a commercial source to spacecraft customers around the world to purchase directly from the company awarded the NASA contract to build these systems. A few years ago, NASA was driven to provide more ground station capacity for spacecraft telemetry, tracking, and command (TT&C) services with a decreasing budget. NASA also made a decision to develop many smaller, cheaper satellites rather than a few large spacecraft as done in the past. In addition, university class missions were being driven to provide their own TT&C services due to the increasing load on the NASA ground-tracking network. NASA's solution for this ever increasing load was to use the existing large aperture systems to support those missions requiring that level of performance and to support the remainder of the missions with the autonomous LEO-T systems. The LEO-T antenna system is a smaller, cheaper, and fully autonomous unstaffed system that can operate without the existing NASA support infrastructure. The LEO-T provides a low-cost, reliable space communications service to the expanding number of low-earth orbiting missions around the world. The system is also fostering developments that improve cost-effectiveness of autonomous-class capabilities for NASA and commercial space use. NASA has installed three LEO-T systems. One station is at the University of Puerto Rico, the second system is installed at the Poker Flat Research Range near Fairbanks, Alaska, and the third system is installed at NASA's Wallops Flight Facility in Virginia. This paper will describe the current NASA implementation of the LEO-T network of antenna systems, the customers now being supported, and the services NASA can now offer with this new breed of autonomous ground stations. In addition, the paper will define the technical capabilities of the system and the cost effectiveness of using the systems including the capital costs of installation.

Kremer, Steven E.; Bundick, Steven N.

1999-01-01

300

Orbiter Camera Payload System  

NASA Technical Reports Server (NTRS)

Components for an orbiting camera payload system (OCPS) include the large format camera (LFC), a gas supply assembly, and ground test, handling, and calibration hardware. The LFC, a high resolution large format photogrammetric camera for use in the cargo bay of the space transport system, is also adaptable to use on an RB-57 aircraft or on a free flyer satellite. Carrying 4000 feet of film, the LFC is usable over the visible to near IR, at V/h rates of from 11 to 41 milliradians per second, overlap of 10, 60, 70 or 80 percent and exposure times of from 4 to 32 milliseconds. With a 12 inch focal length it produces a 9 by 18 inch format (long dimension in line of flight) with full format low contrast resolution of 88 lines per millimeter (AWAR), full format distortion of less than 14 microns and a complement of 45 Reseau marks and 12 fiducial marks. Weight of the OCPS as supplied, fully loaded is 944 pounds and power dissipation is 273 watts average when in operation, 95 watts in standby. The LFC contains an internal exposure sensor, or will respond to external command. It is able to photograph starfields for inflight calibration upon command.

1980-01-01

301

Lifetimes of lunar satellite orbits  

NASA Technical Reports Server (NTRS)

The Space Exploration Initiative has generated a renewed interest in lunar mission planning. The lunar missions currently under study, unlike the Apollo missions, involve long stay times. Several lunar gravity models have been formulated, but mission planners do not have enough confidence in the proposed models to conduct detailed studies of missions with long stay times. In this report, a particular lunar gravitational model, the Ferrari 5 x 5 model, was chosen to determine the lifetimes for 100-km and 300-km perilune altitude, near-circular parking orbits. The need to analyze orbital lifetimes for a large number of initial orbital parameters was the motivation for the formulation of a simplified gravitational model from the original model. Using this model, orbital lifetimes were found to be heavily dependent on the initial conditions of the nearly circular orbits, particularly the initial inclination and argument of perilune. This selected model yielded lifetime predictions of less than 40 days for some orbits, and other orbits had lifetimes exceeding a year. Although inconsistencies and limitations are inherent in all existing lunar gravity models, primarily because of a lack of information about the far side of the moon, the methods presented in this analysis are suitable for incorporating the moon's nonspherical gravitational effects on the preliminary design level for future lunar mission planning.

Meyer, Kurt W.; Buglia, James J.; Desai, Prasun N.

1994-01-01

302

Radiation therapy for orbital lymphoma  

SciTech Connect

Purpose: To describe radiation techniques and evaluate outcomes for orbital lymphoma. Methods and Materials: Forty-six patients (and 62 eyes) with orbital lymphoma treated with radiotherapy between 1987 and 2003 were included. The majority had mucosa-associated lymphoid tissue (48%) or follicular (30%) lymphoma. Seventeen patients had prior lymphoma at other sites, and 29 had primary orbital lymphoma. Median follow-up was 46 months. Results: The median dose was 30.6 Gy; one-third received <30 Gy. Electrons were used in 9 eyes with disease confined to the conjunctiva or eyelid, and photons in 53 eyes with involvement of intraorbital tissues to cover entire orbit. Local control rate was 98% for all patients and 100% for those with indolent lymphoma. Three of the 26 patients with localized primary lymphoma failed distantly, resulting in a 5-year freedom-from-distant-relapse rate of 89%. The 5-year disease-specific and overall survival rates were 95% and 88%, respectively. Late toxicity was mainly cataract formation in patients who received radiation without lens block. Conclusions A dose of 30 Gy is sufficient for indolent orbital lymphoma. Distant relapse rate in patients with localized orbital lymphoma was lower than that reported for low-grade lymphoma presenting in other sites. Orbital radiotherapy can be used for salvage of recurrent indolent lymphoma.

Zhou Ping [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)]. E-mail: pzhou@partners.org; Ng, Andrea K. [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Silver, Barbara [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Li Sigui [Department of Biostatistical Sciences, Dana-Farber Cancer Institute, Boston, MA (United States); Hua Ling [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Mauch, Peter M. [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)

2005-11-01

303

Meteoroid and orbital debris shielding on the Orbital Maneuvering Vehicle  

NASA Technical Reports Server (NTRS)

NASA's Orbital Maneuvering Vehicle (OMV) is being designed to withstand a 10-year lifetime in polar and low earth orbits. A large percentage of OMV's lifetime will be spent operating in the vicinity of the Space Shuttle and Space Station or in storage at these manned locations. An extensive analysis has been performed to determine the effects of the meteoroid and orbital debris environments on OMV's external fuel tanks. A finite element model of OMV was constructed using NASTRAN and analyzed with the meteoroid and debris design analysis code BUMPER. The results show that the long design lifetime, and the ever increasing man-made orbital debris environment, will require the use of shielding over the external fuel tanks.

Kirkpatrick, Marc E.

1989-01-01

304

Orbiter Crew Compartment Integration-Stowage  

NASA Technical Reports Server (NTRS)

This viewgraph presentation describes the Orbiter Crew Compartment Integration (CCI) stowage. The evolution of orbiter crew compartment stowage volume is also described, along with photographs presented of the on-orbit volume stowage capacity.

Morgan, L. Gary

2007-01-01

305

Thirteenth satellite of Jupiter. [orbit determination  

NASA Technical Reports Server (NTRS)

The discovery, observations, and attempts to determine the orbit of Jupiter XIII are described. It is found that the orbit is very similar to the orbits of Jupiter VI, VII, and X. An ephemeris is provided for the 1975 opposition.

Kowal, C. T.; Aksnes, K.; Marsden, B. G.; Roemer, E.

1975-01-01

306

Orbit Correction Implementation at CEBAF  

SciTech Connect

CEBAF has recently performed automated beam orbit control in real time. This effort was achieved by exploiting the capabilities of the TACL control system, using the newly implemented STAR network, which easily yielded the required data transfer density needed. Also involved in this effort was the On-Line Envelope code OLE, which provided first-order transfer matrices that reflected the current machine optics. These tools made the implementation of the specific orbit-correction algorithms easier and increased reliability. The implemented algorithms include beamthreading, orbit-locks with 2 correctors/2 monitors, most-effective corrector, and eta-corrector/eta-monitor correction.

M. Bickley; B.A. Bowling; D. Douglas; A. Hofler; J. Kewisch; G.A. Krafft

1993-05-01

307

Orbital, Rotational, and Climatic Interactions  

NASA Technical Reports Server (NTRS)

The report of an international meeting on the topic of Orbital, Rotational, and Climatic Interactions, which was held 9-11 Jul. 1991 at the Johns Hopkins University is presented. The meeting was attended by 22 researchers working on various aspects of orbital and rotational dynamics, paleoclimate data analysis and modeling, solid-Earth deformation studies, and paleomagnetic analyses. The primary objective of the workshop was to arrive at a better understanding of the interactions between the orbital, rotational, and climatic variations of the Earth. This report contains a brief introduction and 14 contributed papers which cover most of the topics discussed at the meeting.

Bills, Bruce G. (editor)

1992-01-01

308

Extrasolar Planet Orbits and Eccentricities  

E-print Network

The known extrasolar planets exhibit many interesting and surprising features--extremely short-period orbits, high-eccentricity orbits, mean-motion and secular resonances, etc.--and have dramatically expanded our appreciation of the diversity of possible planetary systems. In this review we summarize the orbital properties of extrasolar planets. One of the most remarkable features of extrasolar planets is their high eccentricities, far larger than seen in the solar system. We review theoretical explanations for large eccentricities and point out the successes and shortcomings of existing theories.

Scott Tremaine; Nadia L. Zakamska

2003-12-01

309

Simulation of precise orbit determination of lunar orbiters  

Microsoft Academic Search

Based on the ongoing Chinese lunar exploration mission, i.e. the “Chang'e 1” project, precise orbit determination of lunar orbiters is analyzed for the actual geographical distribution and observational accuracy of the Chinese united S-band (USB) observation and control network as well as the very long baseline interferometry (VLBI) tracking network. The observed data are first simulated, then solutions are found

Xiao-Gong Hu; Cheng Huang; Yong Huang

2005-01-01

310

Simulation of precise orbit determination of lunar orbiters  

NASA Astrophysics Data System (ADS)

Based on the ongoing Chinese lunar exploration mission, i.e. the "Chang'e 1" project, precise orbit determination of lunar orbiters is analyzed for the actual geographical distribution and observational accuracy of the Chinese united S-band (USB) observation and control network as well as the very long baseline interferometry (VLBI) tracking network. The observed data are first simulated, then solutions are found after including the effects of various error sources and finally compared. We use the space data analysis software package, GEODYN, developed at Goddard Space Flight Center, NASA, USA. The primary error source of the flight orbiting the moon is the lunar gravity field. Therefore, the (formal) error of JGL165P1, i.e. the model of the lunar gravity field with the highest accuracy at present, is first discussed. After simulating the data of ranging and velocity measurement as well as the VLBI data of the time delay and time delay rate, precise orbit determination is carried out when the error of the lunar gravity field is added in. When the orbit is determined, the method of reduced dynamics is adopted with the selection of appropriate empirical acceleration parameters to absorb the effect of errors in the lunar gravity field on the orbit determination. The results show that for lunar missions like the "Chang'e 1" project, that do not take the lunar gravity field as their main scientific objective, the method of reduced dynamics is a simple and effective means of improving the accuracy of the orbit determination of the lunar orbiters.

Hu, Xiao-gong; Huang, Cheng; Huang, Yong

2005-10-01

311

The 2006 Orionid outburst imaged by all-sky CCD cameras from Spain: meteoroid spatial fluxes and orbital elements  

NASA Astrophysics Data System (ADS)

By using high-resolution low-scan-rate all-sky CCD cameras, the SPanish Meteor Network (SPMN) detected an outburst of Orionid meteors associated with comet 1P/Halley on 2006 October 20-21. This detection was made possible due to the operational concept of the SPMN that involves continuous monitoring of meteor activity throughout the year. Accurate heliocentric orbits have been obtained for three meteors imaged simultaneously from two stations during the outburst. Additional astrometry of 33 single-station meteors indicates that the activity was produced from a conspicuous geocentric radiant located at ? = 922 +/- 05 and ? = +154 +/- 06 which is similar to the radiant observed during the 1993 Orionid outburst despite the fact that the last one peaked on a different date. The radiant position obtained by the SPMN is consistent with that derived from digital pictures taken a few hours before from Ankara (Turkey). The extent of the outburst (a background of bright meteors was observed over several days), its absence in other years, and the orbital period of the three Orionid orbits suggest that the outburst could be produced by meteoroids trapped in resonances with Jupiter but additional data are required. The SPMN's continuous coverage of meteor activity allowed the identification of the main sources of meteors during 2006 October: mostly due to the Orionid stream, the two branches of the Taurid stream associated with comet 2P/Encke, and the ? Aurigids. Surprisingly, once a detailed analysis of the double-station video meteors was completed, some additional minor stream activity was discovered, that is, the ? Aurigids. In consequence, we also present two accurate orbits of this unexpected, but previously identified, minor shower.

Trigo-Rodríguez, Josep M.; Madiedo, José M.; Llorca, Jordi; Gural, Peter S.; Pujols, Pep; Tezel, Tunc

2007-09-01

312

JSC Orbital Debris Website Description  

NASA Technical Reports Server (NTRS)

Purpose: The website provides information about the NASA Orbital Debris Program Office at JSC, which is the lead NASA center for orbital debris research. It is recognized world-wide for its leadership in addressing orbital debris issues. The NASA Orbital Debris Program Office has taken the international lead in conducting measurements of the environment and in developing the technical consensus for adopting mitigation measures to protect users of the orbital environment. Work at the center continues with developing an improved understanding of the orbital debris environment and measures that can be taken to control its growth. Major Contents: Orbital Debris research is divided into the following five broad efforts. Each area of research contains specific information as follows: 1) Modeling - NASA scientists continue to develop and upgrade orbital debris models to describe and characterize the current and future debris environment. Evolutionary and engineering models are described in detail. Downloadable items include a document in PDF format and executable software. 2) Measurements - Measurements of near-Earth orbital debris are accomplished by conducting ground-based and space-based observations of the orbital debris environment. The data from these sources provide validation of the environment models and identify the presence of new sources. Radar, optical and surface examinations are described. External links to related topics are provided. 3) Protection - Orbital debris protection involves conducting hypervelocity impact measurements to assess the risk presented by orbital debris to operating spacecraft and developing new materials and new designs to provide better protection from the environment with less weight penalty. The data from this work provides the link between the environment defined by the models and the risk presented by that environment to operating spacecraft and provides recommendations on design and operations procedures to reduce the risk as required. These data also help in the analysis and interpretation of impact features on returned spacecraft surfaces. 4) Mitigation - Controlling the growth of the orbital debris population is a high priority for NASA, the United States, and the major space-faring nations of the world to preserve near-Earth space for future generations. Mitigation measures can take the form of curtailing or preventing the creation of new debris, designing satellites to withstand impacts by small debris, and implementing operational procedures ranging from utilizing orbital regimes with less debris, adopting specific spacecraft attitudes, and even maneuvering to avoid collisions with debris. Downloadable items include several documents in PDF format and executable software.and 5) Reentry - Because of the increasing number of objects in space, NASA has adopted guidelines and assessment procedures to reduce the number of non-operational spacecraft and spent rocket upper stages orbiting the Earth. One method of postmission disposal is to allow reentry of these spacecraft, either from orbital decay (uncontrolled entry) or with a controlled entry. Orbital decay may be achieved by firing engines to lower the perigee altitude so that atmospheric drag will eventually cause the spacecraft to enter. However, the surviving debris impact footprint cannot be guaranteed to avoid inhabited landmasses. Controlled entry normally occurs by using a larger amount of propellant with a larger propulsion system to drive the spacecraft to enter the atmosphere at a steeper flight path angle. It will then enter at a more precise latitude, longitude, and footprint in a nearly uninhabited impact region, generally located in the ocean.

Johnson, Nicholas L.

2006-01-01

313

Reactionless orbital propulsion using tether deployment  

NASA Technical Reports Server (NTRS)

Examples of tether propulsion in orbit without the use of reaction mass are discussed. These include (1) using tether extension to reposition a satellite in orbit without fuel expenditure by extending a mass on the end of the tether; (2) using a tether for eccentricity pumping to add energy to the orbit for boosting and orbital transfer; and (3) length modulation of a spinning tether to transfer angular momentum between the orbit and tether spin, thus allowing changes in orbital angular momentum.

Landis, Geoffrey A.

1990-01-01

314

Independent Orbiter Assessment (IOA): Analysis of the orbital maneuvering system  

NASA Technical Reports Server (NTRS)

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The independent analysis results for the Orbital Maneuvering System (OMS) hardware are documented. The OMS provides the thrust to perform orbit insertion, orbit circularization, orbit transfer, rendezvous, and deorbit. The OMS is housed in two independent pods located one on each side of the tail and consists of the following subsystems: Helium Pressurization; Propellant Storage and Distribution; Orbital Maneuvering Engine; and Electrical Power Distribution and Control. The IOA analysis process utilized available OMS hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluted and analyzed for possible failure modes and effects. Criticality was asigned based upon the severity of the effect for each failure mode.

Prust, C. D.; Paul, D. J.; Burkemper, V. J.

1987-01-01

315

M-Dwarfs at Large Heliocentric Distances  

Microsoft Academic Search

We present an analysis of the faint M star population seen as foreground\\u000acontaminants in deep extragalactic surveys. We use space-based data to separate\\u000asuch stars from high redshift galaxies in a publically-available dataset, and\\u000aconsider the photometric properties of the resulting sample in the optical and\\u000ainfrared. The inferred distances place these stars well beyond the scale height\\u000aof

Elizabeth R. Stanway; Malcolm N. Bremer; Matthew D. Lehnert; John J. Eldridge

2007-01-01

316

Count Bowell at record heliocentric distance  

Microsoft Academic Search

New observations of Comet Bowell at the record distance of 13.6 AU are presented. An extended coma is present, the size of which is consistent with the same slow expansion rate of roughly 1 m\\/s detected around perihelion. The cross-section of the solid grains within the central 10 arcsec of the coma has decreased by over an order of magnitude

K. J. Meech; David Jewitt

1987-01-01

317

Two stage to orbit design  

NASA Technical Reports Server (NTRS)

A preliminary design of a two-stage to orbit vehicle was conducted with the requirements to carry a 10,000 pound payload into a 300 mile low-earth orbit using an airbreathing first stage, and to take off and land unassisted on a 15,000 foot runway. The goal of the design analysis was to produce the most efficient vehicle in size and weight which could accomplish the mission requirements. Initial parametric analysis indicated that the weight of the orbiter and the transonic performance of the system were the two parameters that had the largest impact on the design. The resulting system uses a turbofan ramjet powered first stage to propel a scramjet and rocket powered orbiter to the stage point of Mach 6 to 6.5 at an altitude of 90,000 ft.

1991-01-01

318

Pioneer Venus Orbiter Fluxgate Magnetometer  

Microsoft Academic Search

The fluxgate magnetometer on the Pioneer Venus orbiter spacecraft is described. Special features include gradiometer operation, on board despinning, a floating point processor and variable Nyquist filters. Initial operations have been entirely successful.

C. T. Russell; R. C. Snare; J. D. Means; R. C. Elphic

1980-01-01

319

How to Orbit the Earth.  

ERIC Educational Resources Information Center

Discusses the geometry, algebra, and logic involved in the solution of a "Mindbenders" problem in "Discover" magazine and applies it to calculations of satellite orbital velocity. Extends the solution of this probe to other applications of falling objects. (JM)

Quimby, Donald J.

1984-01-01

320

A Case of Orbital Histoplasmosis.  

PubMed

Histoplasma capsulatum var capsulatum is a dimorphic fungus endemic to the Ohio and Mississippi River Valleys of the United States. In this case report, a 33-year-old woman who presented with a right orbital mass causing progressive vision loss, diplopia, and facial swelling is described. Lateral orbitotomy with lateral orbital wall bone flap was performed for excisional biopsy of the lesion. The 1.5 × 1.8 × 2.3 cm cicatricial mass demonstrated a granulomatous lesion with necrosis and positive staining consistent with Histoplasma capsulatum var capsulatum infection. To the authors' knowledge, this is the first case of orbital histoplasmosis to be reported in the United States and the first case worldwide of orbital histoplasmosis due to Histoplasma capsulatum var capsulatum. PMID:25186215

Krakauer, Mark; Prendes, Mark Armando; Wilkes, Byron; Lee, Hui Bae Harold; Fraig, Mostafa; Nunery, William R

2014-09-01

321

NASA Orbital Debris Baseline Populations  

NASA Technical Reports Server (NTRS)

The NASA Orbital Debris Program Office has created high fidelity populations of the debris environment. The populations include objects of 1 cm and larger in Low Earth Orbit through Geosynchronous Transfer Orbit. They were designed for the purpose of assisting debris researchers and sensor developers in planning and testing. This environment is derived directly from the newest ORDEM model populations which include a background derived from LEGEND, as well as specific events such as the Chinese ASAT test, the Iridium 33/Cosmos 2251 accidental collision, the RORSAT sodium-potassium droplet releases, and other miscellaneous events. It is the most realistic ODPO debris population to date. In this paper we present the populations in chart form. We describe derivations of the background population and the specific populations added on. We validate our 1 cm and larger Low Earth Orbit population against SSN, Haystack, and HAX radar measurements.

Krisko, Paula H.; Vavrin, A. B.

2013-01-01

322

Lunar orbital mass spectrometer experiment  

NASA Technical Reports Server (NTRS)

The design, development, manufacture, test and calibration of five lunar orbital mass spectrometers with the four associated ground support equipment test sets are discussed. A mass spectrometer was installed in the Apollo 15 and one in the Apollo 16 Scientific Instrument Module within the Service Module. The Apollo 15 mass spectrometer was operated with collection of 38 hours of mass spectra data during lunar orbit and 50 hours of data were collected during transearth coast. The Apollo 16 mass spectrometer was operated with collection of 76 hours of mass spectra data during lunar orbit. However, the Apollo 16 mass spectrometer was ejected into lunar orbit upon malfunction of spacecraft boom system just prior to transearth insection and no transearth coast data was possible.

Lord, W. P.

1971-01-01

323

Orbital servicing of space platforms  

NASA Technical Reports Server (NTRS)

NASA-MSFC is planning systems for the orbital servicing and maintenance of large geosynchronous platforms. The goal is to devise methods to maintain, update, and/or replace the basic spacecraft housekeeping equipment as well as the onboard mission equipment. The planning has passed through the feasibility demonstration level. A hard engineering test unit of such an on-orbit servicing system, complete with control system, is being tested and evaluated by MSFC.

Turner, J. R.; Derocher, W. L., Jr.

1978-01-01

324

Orbits in a logarithmic potential  

SciTech Connect

The characteristics of charged particle orbits in the logarithmic electrostatic potential field surrounding a straight conducting wire at a fixed potential are investigated. The equations of motion of an electron in a logarithmic potential are derived, the limiting cases are considered, and the results of numerical integration of the equations of motion are presented along with sketches of a few representative orbits. (C.E.S.)

Hooverman, R.H.

2014-04-15

325

Multimodality imaging of the orbit  

PubMed Central

The role of imaging is well established in the evaluation of orbital diseases. Ultrasonography, Computed tomography and Magnetic resonance imaging are complementary modalities, which allow direct visualization of regional anatomy, accurate localization and help to characterize lesions to make a reliable radiological diagnosis. The purpose of this pictorial essay is to highlight the imaging features of commonly encountered pathologies which involve the orbit. PMID:23599570

Hande, Pradipta C; Talwar, Inder

2012-01-01

326

Follicular lymphoma involving the orbit.  

PubMed

Non-Hodgkin's lymphoma is the fifth most common malignancy, with an annual incidence in the UK of 8/100,000. Until recently this incidence had been rising over the past two decades. The WHO classification divides non-Hodgkin's lymphomas into B- or T-cell neoplasms, with 85% of general lymphomas and almost all orbital lymphomas consisting of B-cell tumours. A case of systemic follicular lymphoma, with later orbital involvement, is presented. PMID:17984509

Yap, Yew Chong; Ardeshna, Kirit; Kosmin, Alan; Rose, Geoffrey E

2007-01-01

327

Precise orbit determination for GRACE  

NASA Astrophysics Data System (ADS)

The twin, co-orbiting GRACE (Gravity Recovery and Climate Experiment) satellites were launched in March 2002. The primary objective of the GRACE mission is to determine the Earth's gravity field and its temporal variations with unprecedented accuracy. To satisfy this objective as well as other applications (e.g. atmospheric profiling by radio occultation), accurate orbits for GRACE are required. This paper describes several results related to the use of the data collected by the GRACE GPS receiver, high precision accelerometer observations and precise attitude data from star trackers in the application of the GRACE Precise Orbit Determination (POD). The orbit accuracy is assessed using a number of tests, which include analysis of GPS tracking observation residuals, Satellite Laser Ranging (SLR) residuals, K-Band Ranging (KBR) residuals and external orbit comparisons. The results show that an accuracy of better than 5 cm in each direction for GRACE orbits can be obtained. The relative accuracy of the two GRACE satellites is about 1 cm in position and 10 micrometers per second in velocity.

Kang, Z.; Nagel, P.; Pastor, R.

2003-04-01

328

Low Earth orbit communications satellite  

NASA Technical Reports Server (NTRS)

A current thrust in satellite communication systems considers a low-Earth orbiting constellations of satellites for continuous global coverage. Conceptual design studies have been done at the time of this design project by LORAL Aerospace Corporation under the program name GLOBALSTAR and by Motorola under their IRIDIUM program. This design project concentrates on the spacecraft design of the GLOBALSTAR low-Earth orbiting communication system. Overview information on the program was gained through the Federal Communications Commission licensing request. The GLOBALSTAR system consists of 48 operational satellites positioned in a Walker Delta pattern providing global coverage and redundancy. The operational orbit is 1389 km (750 nmi) altitude with eight planes of six satellites each. The orbital planes are spaced 45 deg., and the spacecraft are separated by 60 deg. within the plane. A Delta 2 launch vehicle is used to carry six spacecraft for orbit establishment. Once in orbit, the spacecraft will utilize code-division multiple access (spread spectrum modulation) for digital relay, voice, and radio determination satellite services (RDSS) yielding position determination with accuracy up to 200 meters.

Moroney, D.; Lashbrook, D.; Mckibben, B.; Gardener, N.; Rivers, T.; Nottingham, G.; Golden, B.; Barfield, B.; Bruening, J.; Wood, D.

1992-01-01

329

Harmonic structure of generic Kerr orbits  

NASA Astrophysics Data System (ADS)

Generic Kerr orbits exhibit intricate three-dimensional motion. We offer a classification scheme for these intricate orbits in terms of periodic orbits. The crucial insight is that for a given effective angular momentum L and angle of inclination ?, there exists a discrete set of orbits that are geometrically n-leaf clovers in a precessing orbital plane. When viewed in the full three dimensions, these orbits are periodic in r-?. Each n-leaf clover is associated with a rational number, 1+qr?=??/?r, that measures the degree of perihelion precession in the precessing orbital plane. The rational number qr? varies monotonically with the orbital energy and with the orbital eccentricity. Since any bound orbit can be approximated as near one of these periodic n-leaf clovers, this special set offers a skeleton that illuminates the structure of all bound Kerr orbits, in or out of the equatorial plane.

Grossman, Rebecca; Levin, Janna; Perez-Giz, Gabe

2012-01-01

330

Astrometric planet search around southern ultracool dwarfs III. Discovery of a brown dwarf in a 3-year orbit around DE0630-18  

E-print Network

Using astrometric measurements obtained with the FORS2/VLT camera, we are searching for low-mass companions around 20 nearby ultracool dwarfs. With a single-measurement precision of 0.1 milli-arcseconds, our survey is sensitive to a wide range of companion masses from planetary companions to binary systems. Here, we report the discovery and orbit characterisation of a new ultracool binary at a distance of 19.5 pc from Earth that is composed of the M8.5-dwarf primary DE0630-18 and a substellar companion. The nearly edge-on orbit is moderately eccentric (e=0.23) with an orbital period of 1120 d, which corresponds to a relative separation in semimajor axis of approximately 1.1 AU. We obtained a high-resolution optical spectrum with UVES/VLT and measured the system's heliocentric radial velocity. The spectrum does not exhibit lithium absorption at 670.8 nm, indicating that the system is not extremely young. A preliminary estimate of the binary's physical parameters tells us that it is composed of a primary at the...

Sahlmann, J; Segransan, D; Martin, E L; Mayor, M; Queloz, D; Udry, S

2015-01-01

331

Orbital Evolution of ExtraSolar Giant Planets  

Microsoft Academic Search

The recent discoveries (Mayor and Queloz, 1995; Marcy and Butler, 1996; Butler and Marcy, 1996) of extra-solar giant planets (EGPs) at small heliocentric distances have prompted questions about the formation, evolution, and migration of these EGPs. The location of several EGPs at much less than 1 AU from their primaries has proved to be particularly problematic. Since it is thought

D. E. Trilling; W. Benz; T. Guillot; J. I. Lunine

1996-01-01

332

Space Tourism: Orbital Debris Considerations  

NASA Astrophysics Data System (ADS)

Space activities after a phase of research and development, political competition and national prestige have entered an era of real commercialization. Remote sensing, earth observation, and communication are among the areas in which this growing industry is facing competition and declining government money. A project like International Space Station, which draws from public money, has not only opened a window of real multinational cooperation, but also changed space travel from a mere fantasy into a real world activity. Besides research activities for sending man to moon and Mars and other outer planets, space travel has attracted a considerable attention in recent years in the form of space tourism. Four countries from space fairing nations are actively involved in the development of space tourism. Even, nations which are either in early stages of space technology development or just beginning their space activities, have high ambitions in this area. This is worth noting considering their limited resources. At present, trips to space are available, but limited and expensive. To move beyond this point to generally available trips to orbit and week long stays in LEO, in orbital hotels, some of the required basic transportations, living requirements, and technological developments required for long stay in orbit are already underway. For tourism to develop to a real everyday business, not only the price has to come down to meaningful levels, but also safety considerations should be fully developed to attract travelers' trust. A serious hazard to space activities in general and space tourism in particular is space debris in earth orbit. Orbiting debris are man-made objects left over by space operations, hazardous to space missions. Since the higher density of debris population occurs in low earth orbit, which is also the same orbit of interest to space tourism, a careful attention should be paid to the effect of debris on tourism activities. In this study, after a review of the current work on space tourism and debris situation in low earth orbit suitable orbits for space tourism activities with regard to the presence of orbital debris are discussed.

Mahmoudian, N.; Shajiee, S.; Moghani, T.; Bahrami, M.

2002-01-01

333

An Orbit Propagation Software for Mars Orbiting Spacecraft  

NASA Astrophysics Data System (ADS)

An orbit propagation software for the Mars orbiting spacecraft has been developed and verified in preparations for the future Korean Mars missions. Dynamic model for Mars orbiting spacecraft has been studied, and Mars centered coordinate systems are utilized to express spacecraft state vectors. Coordinate corrections to the Mars centered coordinate system have been made to adjust the effects caused by Mars precession and nutation. After spacecraft enters Sphere of Influence (SOI) of the Mars, the spacecraft experiences various perturbation effects as it approaches to Mars. Every possible perturbation effect is considered during integrations of spacecraft state vectors. The Mars50c gravity field model and the Mars-GRAM 2001 model are used to compute perturbation effects due to Mars gravity field and Mars atmospheric drag, respectively. To compute exact locations of other planets, JPL's DE405 ephemerides are used. Phobos and Deimos's ephemeris are computed using analytical method because their informations are not released with DE405. Mars Global Surveyor's mapping orbital data are used to verify the developed propagator performances. After one Martian day propagation (12 orbital periods), the results show about maximum ±5 meter errors, in every position state components(radial, cross-track and along-track), when compared to these from the Astrogator propagation in the Satellite Tool Kit. This result shows high reliability of the developed software which can be used to design near Mars missions for Korea, in future.

Song, Young-Joo; Park, Eun-Seo; Yoo, Sung-Moon; Park, Sang-Young; Choi, Kyu-Hong; Yoon, Jae-Cheol; Yim, Jo-Ryeong; Kim, Han-Dol; Choi, Jun-Min; Kim, Hak-Jung; Kim, Byung-Kyo

2004-12-01

334

Binary asteroid orbit expansion due to continued YORP spin-up of the primary and primary surface particle motion  

NASA Astrophysics Data System (ADS)

We examine the hypothesis that within close binary asteroid systems with super-synchronously rotating, roughly spheroidal primary (Alpha) and synchronous elongated secondary (Beta), continued YORP angular acceleration of the primary causes it to spin at rates where loose material near its equator is lofted from the surface. Subsequent interaction of the material with the binary components causes that material to lose angular momentum and re-impact Alpha. In this process angular momentum is transferred to the orbit, causing the orbit to expand. We confirm this hypothesis through precise dynamic and approximate statistical simulation. For this we use the well-characterized 1999 KW4 system model, as KW4 typifies the class of binaries of interest. Our results visibly demonstrate the transfer of angular momentum and the hypothesized orbit evolution mechanism. In particular, we observe regulation of Alpha spin rate at the rate for which material lofting begins on the same side of Alpha as Beta, but not yet on the opposite side. We observe nearly constant Alpha angular momentum while the orbit angular momentum grows steadily. The linear fit to that growth is consistent with the YORP torque angular acceleration applied. Lofting occurs in fast transient episodes separated by long periods of slow spin-up under that acceleration. The average amount of material aloft and rate of mass lofting are interesting metrics for the system's lofting activity level contained in our results, but are not physically descriptive at any particular instant, given episodic lofting. We translate the orbit angular momentum growth to average semi-major axis change rate with a simple formula, whose integration also leads to time scales for the system evolution several times faster than standard tidal evolution (such as present orbit size doubling time of 2.5 ± 0.7 Myr for KW4). The observationally-supported end state of the system's evolution is likely separation into two asteroids on closely-related heliocentric orbits. Possible shedding of sufficiently more material from the still YORP-torqued primary may form a new secondary and repeat the overall system evolution.

Fahnestock, Eugene G.; Scheeres, Daniel J.

2009-05-01

335

ORBITAL PHASE IN INSPIRALLING COMPACT BINARIES  

Microsoft Academic Search

We derive the rate of change of the mean motion up to the second post-Newtonian order for inspiralling compact binaries with spin, mass quadrupole and magnetic dipole moments on eccentric orbits. We give this result in terms of orbital elements. We also present the related orbital phase for circular orbits. Observations by Earth-based gravitational wave observatories are under way aiming

AS VAS ´; BAL ´ AZS MIK

336

New Perspectives on Orbitally Forced Stratigraphy  

Microsoft Academic Search

This survey of the current status of research into Earth's orbitally forced paleoclimatic record summarizes recent developments in the theory of Earth's orbital parameters, and reviews how various techniques of data collection and analysis have fared in the search and recovery of orbital signals in ancient stratigraphy. The emerging significance of the quasi-periodicity of Earth's orbital variations as a prin-

Linda A. Hinnov

2000-01-01

337

Stable bound orbits around black rings  

SciTech Connect

We examine bound orbits of particles around singly rotating black rings. We show that there exist stable bound orbits in toroidal spiral shape near the 'axis' of the ring, and also stable circular orbits on the axis as special cases. The stable bound orbits can have arbitrary large size if the thickness of the ring is less than a critical value.

Igata, Takahisa; Ishihara, Hideki; Takamori, Yohsuke [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan)

2010-11-15

338

THE ORBITS OF THE OUTER URANIAN SATELLITES  

SciTech Connect

We report on the numerically integrated orbits for the nine outer Uranian satellites. The orbits are calculated based on fits to the astrometric observations for the period from 1984 to 2006. The results include the state vectors, post-fit residuals, and mean orbital elements. We also assess the accuracy of the orbital fits and discuss the need for future measurements.

Brozovic, M.; Jacobson, R. A. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States)], E-mail: marina.brozovic@jpl.nasa.gov

2009-04-15

339

An Analytical Satellite Orbit Predictor (ASOP)  

NASA Technical Reports Server (NTRS)

The documentation and user's guide for the Analytical Satellite Orbit Predictor (ASOP) computer program is presented. The ASOP is based on mathematical methods that represent a new state-of-the-art for rapid orbit computation techniques. It is intended to be used for computation of near-earth orbits including those of the shuttle/orbiter and its payloads.

Starke, S. E.

1977-01-01

340

Model Orbits of Asteroid 3040 Kozai  

Microsoft Academic Search

The orbital evolutions of the asteroid 3040 Kozai and model asteroids with similar orbits have been investigated. Their osculating orbits for an epoch 1991 December 10 were numerically integrated forward within the interval of 20,000 years, using a dynamical model of the solar system consisting of all inner planets, Jupiter, and Saturn. The orbit of the asteroid Kozai is stable.

Nina A. Solovaya; Eduard M. Pittich

1995-01-01

341

Communications satellites in non-geostationary orbits  

NASA Technical Reports Server (NTRS)

The design of a satellite communications system in an orbit lower than GEO is described. Two sun-synchronous orbits which lie in the equatorial plane have been selected: (1) the apogee at constant time-of-day equatorial orbit, a highly eccentric orbit with five revolutions per day, which allows 77-135 percent more satellite mass to be placed in orbit than for GEO; and (2) the sun-synchronous 12-hour equatorial orbit, a circular orbit with two revolutions per day, which allows 23-29 percent more mass. The results of a life cycle economic analysis illustrate that nongeostationary satellite systems could be competitive with geostationary satellite systems.

Price, Kent M.; Doong, Wen; Nguyen, Tuan Q.; Turner, Andrew E.; Weyandt, Charles

1988-01-01

342

Evaluation of viewing periods between orbiting spacecraft  

NASA Technical Reports Server (NTRS)

Communication links between two orbiters are analyzed by projecting occultation regions onto the orbit planes. The occultation regions are conic sections, and can be defined in the same functional form as orbits. Cases of a full and partial ellipse, full, partial, and degenerate hyperbola, and parabola are considered. It is noted that because overall communication link availability may depend on earth-to-orbiter and surface-to-orbiter links, the analysis must consider the simultaneous performance of all links. The approach presented in this study gives insight into the orbiter-to-orbiter geometry and the overall communication link availability.

Meyer, Scott A.

1989-01-01

343

A criterion to classify asteroids and comets based on the orbital parameters  

NASA Astrophysics Data System (ADS)

The classification criterion between asteroids and comets has evolved in recent decades, but the main distinction remains unchanged. Comets present gas and dust ejection from the surface at some point of their orbits, therefore, these objects are considered to be active. On the other hand, asteroids do not show any kind of large scale gas and dust ejection, they are inert. Nevertheless, this classification scheme is impractical when we have more than 500,000 asteroids already discovered. In addition, comets are not active all along their orbits. In order for a comet to display activity at present or in the recent past in the inner region of the Solar System (heliocentric distance <2 AU), the cometary orbit must be unstable in the time scale on the order of ten thousands of years; otherwise, the object should have completely consumed its volatile component. Close encounters with the most massive planets is the only mechanism that could produce “macroscopic” instabilities on a short time scale. The macroscopic changes in the orbital elements can be detected in a numerical integration of the dynamical evolution of the object over a time scale of several thousand years. This procedure to identify asteroids in cometary-like orbits is also impractical because it would require months of computing time. Therefore, a classification scheme based on the orbital elements to identify the border cases between the asteroid and comet populations is urgently required. We present a criterion to classify asteroids and comets and to find the border case based on the Tisserand’s parameter, the Minimum Orbital Intersection Distance (MOID), and considering some information regarding the aphelion and perihelion distances. Objects in mean-motion are disregarded. After applying a filter to the sample of over half a million asteroids already discovered to select the precise orbits and to the sample of 487 short-period comets, we apply the proposed classification criterion. The resulting sample consists of ?331 Asteroids in Cometary Orbits (ACOs). The ACOs are further classified in subclasses similar to the cometary classification. There are 436 Jupiter Family Comets and 203 ACOs of the Jupiter Family type. This new criterion is more strict that the criteria used by other authors to identify ACOs; nonetheless, with the new criterion we ensure that the ACOs have a chaotic dynamical evolution similar to the periodic comets. The discovered dormant or extinct comets seems, if they exist at all, to be a small fraction of the active comets. We also analyse the available photometric data of ACOs to identify possible large brightness variations. Among the sample of ACOs, there is only one object with brightness variations typical of an active comet: 174P/(60558) Echeclus. But this object has already been double classified as asteroid and comet.

Tancredi, Gonzalo

2014-05-01

344

A New NOAO Survey Program: Mutual Orbits and Masses of Kuiper Belt Binaries  

NASA Astrophysics Data System (ADS)

We will report progress from our multi-year campaign to determine the orbits and masses of transneptunian binaries (TNBs). Binary systems are abundant in the Kuiper belt, and especially among the "Cold Classical" disk of objects on low-eccentricity, lowinclination, non-resonant orbits about the Sun [1]. These binaries offer an opportunity to learn the masses and densities of an intriguing population of small, distant objects. Additionally, the statistics of their mutual orbital parameters offer clues to conditions where they formed in the protoplanetary nebula, as well as to subsequent dynamical evolution of the outer solar system. Historically, NASA/ESA's Hubble Space Telescope (HST) has been the premier facility for spatially resolving the components of TNBs, benefiting from its exceptionally stable optics and from diffraction- limited imaging unimpeded by the Earth's atmosphere. More recently, laser guide star adaptive optics (LGS AO) technology has enabled large groundbased telescopes to begin contributing valuable data as well [2]. LGS AO observations of faint TNBs (the components of which have typical V magnitudes ~24th) are only feasible when the target passes near an appulse star suitable for use as a tip-tilt correction reference. We have been using LGS AO data from Keck in combination with HST data to constrain TNB orbits [e.g., 3]. In 2011 we began a new 3-year NOAO Survey program to use LGS AO on the 8 m Gemini North telescope. We will discuss how Gemini and other telescopes complement one another, show examples of data from Gemini, Keck, and HST, and describe how we are using these facilities to improve orbital knowledge for as many of the tighter TNBs as we can. Optimal scheduling techniques enable us to make the most efficient possible use of the very limited availability of time on telescopes capable of resolving these objects [4]. Our progress is documented online at http://www.lowell.edu/~grundy/tnbs. We will discuss systems of particular interest such as those likely to undergo mutual events in the near future. These include 2003 QW111 (events probably beginning in a few years) and 79360 1997 CS29 (events probably happening right now). Also of interest are systems for which sizes can be independently determined from thermal or other observations. For these systems, the dynamical masses from binary orbits enable computation of bulk densities. We will also explore statistical patterns beginning to emerge from the growing ensemble of known TNB orbits. Observed distributions of orbital characteristics, including inclinations, eccentricities, and separations have important implications for formation scenarios as well as subsequent evolution [5], although accounting for observational biases remains an open issue. For instance, there appears to be a shortage of loose binaries among TNOs on excited heliocentric orbits. While there seems to be an excess of prograde systems among the tighter binaries, there is little evidence for preferentially low inclinations.

Grundy, W. M.; Benecchi, S. D.; Buie, M. W.; Noll, K. S.; Porter, S. B.; Roe, H. G.; Stansberry, J. A.; Trujillo, C. A.

2011-10-01

345

Tumor pathology of the orbit.  

PubMed

The term orbital tumor covers a wide range of benign and malignant diseases affecting specific component of the orbit or developing in contact with them. They are found incidentally or may be investigated as part of the assessment of a systemic disorder or because of orbital signs (exophthalmos, pain, etc.). Computed tomography, MRI and Color Doppler Ultrasound (CDU), play a varying role depending on the clinical presentation and the disease being investigated. This article reflects long experience in a reference center but does not claim to be exhaustive. We have chosen to consider these tumors from the perspective of their usual presentation, emphasizing the most common causes and suggestive radiological and clinical presentations (progressive or sudden-onset exophthalmos, children or adults, lacrimal gland lesions, periorbital lesions and enophthalmos). We will describe in particular muscle involvement (thyrotoxicosis and tumors), vascular lesions (cavernous sinus hemangioma, orbital varix, cystic lymphangioma), childhood lesions and orbital hematomas. We offer straightforward useful protocols for simple investigation and differential diagnosis. Readers who wish to go further to extend their knowledge in this fascinating area can refer to the references in the bibliography. PMID:25195185

Héran, F; Bergès, O; Blustajn, J; Boucenna, M; Charbonneau, F; Koskas, P; Lafitte, F; Nau, E; Roux, P; Sadik, J C; Savatovsky, J; Williams, M

2014-10-01

346

The Mars Reconnaissance Orbiter Mission  

NASA Astrophysics Data System (ADS)

The Mars Reconnaissance Orbiter (MRO) will be launched in August 2005 by an Atlas V 401 expendable launch vehicle from Cape Canaveral Air Force Station, USA. It will deliver to Mars orbit a payload to conduct remote sensing science observations, identify and characterize sites for future landers, and provide critical telecom/navigation relay capability for follow-on missions. The mission is designed to provide global, regional survey, and targeted observations from a low 255 km by 320 km Mars orbit with a 3:00 PM local mean solar time (ascending node). During the one Martian year (687 Earth days) primary science phase, the orbiter will acquire visual and near-infrared high-resolution images of the planet's surface, monitor atmospheric weather and climate, and search the upper crust for evidence of water. After this science phase is completed, the orbiter will provide telecommunications support for spacecraft launched to Mars in the 2007 and 2009 opportunities. The primary mission ends on December 31, 2010, approximately 5.5 years after launch.

Graf, James E.; Zurek, Richard W.; Eisen, Howard J.; Jai, Benhan; Johnston, M. D.; Depaula, Ramon

2005-07-01

347

Mars Orbiter Most Likely Lost  

NSDL National Science Digital Library

In an embarrassing setback to NASA, the Mars Climate Orbiter is believed lost. In the early hours of September 23, the orbiter fired its main engine to go in orbit around Mars and passed behind the planet, losing radio contact as planned. However, due to what was most likely a navigation error, the spacecraft did not resume contact and may have flown too close to the atmosphere and broken apart or burned up. The relatively inexpensive ($125 million) Climate Orbiter was launched in December 1998 to become the first interplanetary weather satellite, studying Martian weather for one Mars year (about two Earth years). It was also to serve as a relay station for five years, relaying information to and from the Mars Polar Lander, due to land on December 3, 1999. NASA, however, insists that the Polar Lander's mission can be accomplished independently and "the science return of that mission won't be affected." The sites listed provide information about Mars Climate Orbiter and its possible loss.

de Nie, Michael Willem.

348

The 2009 Mars Telecommunications Orbiter  

NASA Technical Reports Server (NTRS)

The first spacecraft with a primary function of providing communication links while orbiting a foreign planet has begun development for a launch in 2009. NASA's Mars Telecommunications Orbiter would use three radio bands to magnify the benefits of other future Mars missions and enable some types of missions otherwise impractical. It would serve as the Mars hub for a growing interplanetary Internet. And it would pioneer the use of planet-to-planet laser communications to demonstrate the possibility for even greater networking capabilities in the future. With Mars Telecommunications Orbiter overhead in the martian sky, the Mars Science Laboratory rover scheduled to follow the orbiter to Mars by about a month could send to Earth more than 100 times as much data per day as it could otherwise send. The orbiter will be designed for the capability of relaying up to 15 gigabits per day from the rover, equivalent to more than three full compact discs each day. The same benefits would accrue to other future major Mars missions from any nation.

Wilson, G. R.; DePaula, R.; Diehl, R. E.; Edwards, C. D.; Fitzgerald, R. J.; Franklin, S. F.; Kerridge, S. A.; Komarek, T. A.; Noreen, G. K.

2004-01-01

349

Management of the orbital environment  

NASA Technical Reports Server (NTRS)

Data regarding orbital debris are presented to shed light on the requirements of environmental management in space, and strategies are given for active intervention and operational strategies. Debris are generated by inadvertent explosions of upper stages, intentional military explosions, and collisional breakups. Design and operation practices are set forth for minimizing debris generation and removing useless debris from orbit in the low-earth and geosynchronous orbits. Self-disposal options include propulsive maneuvers, drag-augmentation devices, and tether systems, and the drag devices are described as simple and passive. Active retrieval and disposition are considered, and the difficulty is examined of removing small debris. Active intervention techniques are required since pollution prevention is more effective than remediation for the problems of both earth and space.

Loftus, Joseph P., Jr.; Kessler, Donald J.; Anz-Meador, Phillip D.

1991-01-01

350

Orbital resonances in exoplanetary systems  

NASA Astrophysics Data System (ADS)

At present, more than 700 exoplanetary systems are known to have been discovered. They incorporate more than 130 multiplanet systems, i.e. those hosting two or more planets. The orbital resonance and near-resonance phenomena are ubiquitous in them. We present a statistical and dynamical analysis of the resonance structure of the multiplanet systems and planetary systems of binary stars. We have built distributions of the orbital period ratios, separately considering the cases of inner and outer location of the massive perturber. The histograms reveal apparent peaks close to the first order orbital resonances 2/1 and 3/2 in both cases; this confirms previous findings. We have performed analytical modelling of the histograms, and obtained exact positions of the peaks. Moreover, we have built the "period ratio – eccentricity" diagrams, with collision curves superimposed, so that to find anomalous systems.

Popova, E. A.; Shevchenko, I. I.

2014-12-01

351

Orbital extension of trigeminal schwannoma.  

PubMed

Schwannomas, also known as neurilemmomas, are benign peripheral nerve sheath tumors. Trigeminal schwannomas are rare intracranial tumors. Here, we report a 35-year-old female presenting with an axial proptosis of right eyeball with right-sided III, IV and VI cranial nerve palsy. Her best corrected visual acuity in the right eye was perception of light absent and in the left eye was 20/20. MRI scan revealed a large right-sided heterogeneous, extra-axial middle cranial fossa mass that extended to the intraconal space of right orbit. A diagnosis of intracranial trigeminal nerve schwannoma with right orbital extension was made. Successful surgical excision of the mass with preservation of the surrounding tissues and orbital exenteration was done. Post-operative period was uneventful. PMID:25552864

Ghosh, Shantanu; Das, Debabrata; Varshney, Rahul; Nandy, Sumit

2015-01-01

352

Orbital extension of trigeminal schwannoma  

PubMed Central

Schwannomas, also known as neurilemmomas, are benign peripheral nerve sheath tumors. Trigeminal schwannomas are rare intracranial tumors. Here, we report a 35-year-old female presenting with an axial proptosis of right eyeball with right-sided III, IV and VI cranial nerve palsy. Her best corrected visual acuity in the right eye was perception of light absent and in the left eye was 20/20. MRI scan revealed a large right-sided heterogeneous, extra-axial middle cranial fossa mass that extended to the intraconal space of right orbit. A diagnosis of intracranial trigeminal nerve schwannoma with right orbital extension was made. Successful surgical excision of the mass with preservation of the surrounding tissues and orbital exenteration was done. Post-operative period was uneventful. PMID:25552864

Ghosh, Shantanu; Das, Debabrata; Varshney, Rahul; Nandy, Sumit

2015-01-01

353

The Challenge of Orbital Debris  

NASA Technical Reports Server (NTRS)

Since the dawn of the Space Age more than 50 years ago, humans have been launching objects into the space environment faster than they have been removed by active means or natural decay. This has led to a proliferation of debris -- derelict satellites, discarded rocket upper stages, and pieces from satellite breakups -- in Earth orbit, especially in well-used orbital regimes. This talk will summarize the current knowledge of the debris environment and describe plans to address the challenges orbital debris raises for the future usability of near-Earth space. The talk will be structured around 4 categories: Measurements, Modeling, Shielding, and Mitigation. This will include discussions of the long-term prognosis of debris growth (i.e., the "Kessler Syndrome") as well as plans for active debris removal.

Matney, Mark

2012-01-01

354

Orbit of 1976 AA. [asteroid  

NASA Technical Reports Server (NTRS)

The orbit of Asteroid 1976 AA is described, with attention given to calculations of its period and its distance from earth, both of which could be accurately and quickly determined by measuring the minor planet's position over wide ranges of hour angle on one to three nights. The geometry of the asteroid's orbit is compared to that of earth's orbit, and the periodicity of the minor planet's approaches to earth is projected. The motion of 1976 AA over an interval of seven centuries into both past and future is also studied; the possibility of its libration with respect to earth or to Venus is examined. Some data on closest approaches of the asteroid to Mars and Venus, as well as to earth, are given.

Marsden, B. G.; Williams, J. G.

1977-01-01

355

Orbital resonances around black holes.  

PubMed

We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here. PMID:25768747

Brink, Jeandrew; Geyer, Marisa; Hinderer, Tanja

2015-02-27

356

G-C Orbiting Satellite  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: A satellite orbiting the earth in a circular path stays at a constant altitude of 100 kilometers throughout its orbit. Given that the radius of the ear...

2013-10-14

357

Energy and the Elliptical Orbit  

NASA Astrophysics Data System (ADS)

In the January 2007 issue of The Physics Teacher, Prentis, Fulton, Hesse, and Mazzino describe a laboratory exercise in which students use a geometrical analysis inspired by Newton to show that an elliptical orbit and an inverse-square law force go hand in hand. The historical, geometrical, and teamwork aspects of the exercise are useful and important. This paper presents an exercise which uses an energy/angular momentum conservation model for elliptical orbits. This exercise can be done easily by an individual student and on regular notebook-sized paper.

Nettles, Bill

2009-03-01

358

Orbiter electrical equipment utilization baseline  

NASA Technical Reports Server (NTRS)

The baseline for utilization of Orbiter electrical equipment in both electrical and Environmental Control and Life Support System (ECLSS) thermal analyses is established. It is a composite catalog of Space Shuttle equipment, as defined in the Shuttle Operational Data Book. The major functions and expected usage of each component type are described. Functional descriptions are designed to provide a fundamental understanding of the Orbiter electrical equipment, to insure correlation of equipment usage within nominal analyses, and to aid analysts in the formulation of off-nominal, contingency analyses.

1980-01-01

359

Current Issues in Orbital Debris  

NASA Technical Reports Server (NTRS)

During the past two decades, great strides have been made in the international community regarding orbital debris mitigation. The majority of space-faring nations have reached a consensus on an initial set of orbital debris mitigation measures. Implementation of and compliance with the IADC and UN space debris mitigation guidelines should remain a high priority. Improvements of the IADC and UN space debris mitigation guidelines should continue as technical consensus permits. The remediation of the near-Earth space environment will require a significant and long-term undertaking.

Johnson, Nicholas L.

2011-01-01

360

Orbit and properties of the massive X-ray binary BD +60 73=IGR J00370+6122  

NASA Astrophysics Data System (ADS)

Context. High-energy X-rays generated in massive binary systems can arise from several different mechanisms. Constraints on the orbital parameters of these systems are therefore necessary to properly understand and interpret the X-ray phenomena. Aims: In this study we aim to determine a spectroscopic orbit for the high-mass X-ray binary system BD +60 73=IGR J00370+6122, to infer the properties of the optical and compact companion, and to interpret the characteristics of the X-ray light curve within the context of our findings. Methods: We acquired 123 spectroscopic observations with the David Dunlap Observatory and Kitt Peak National Observatory telescopes in the optical domain. Using a cross-correlation technique, we measured the radial velocity of each of these spectra relative to the heliocentric rest-frame. An orbital solution was obtained from the resulting radial velocity measurements. Spectra of several spectral standards were also acquired to reassess the spectral classification of the optical companion. Results: The best-fit orbital parameters suggest an eccentricity of e = 0.48+0.02-0.03 and a mass-function of f(M) = 0.009 ± 0.002, lending further support to the assumption that the companion is a low-mass compact star. We find that the X-ray maximum occurs just after the time of periastron passage, but before the time of superior conjunction when the optical companion could eclipse the compact companion. The spectrum of the optical companion is best matched by the B1Ib spectral standard HD 24398, which reaffirms the original classification. Conclusions: The mass-function combined with a plausible range of possible masses for a neutron star companion yields primary masses within the range expected for the spectral type of BD +60 73 for high orbital inclinations. The compact companion cannot be a black hole unless the supergiant has an exceptionally high mass for its B1Ib spectral type or if the inclination of its orbit is very low. The X-ray timing and characteristics can potentially be explained by accretion variations on the compact object; but this would require the companion to be a magnetar. Table 2 is available in electronic form at http://www.aanda.org

Grunhut, J. H.; Bolton, C. T.; McSwain, M. V.

2014-03-01

361

Orbital debris sweeper and method  

NASA Technical Reports Server (NTRS)

An orbital debris sweeper is provided for removing particles from orbit which otherwise may impact and damage an orbiting spacecraft. The debris sweeper includes a central sweeper core which carries a debris monitoring unit, and a plurality of large area impact panels rotatable about a central sweeper rotational axis. In response to information from the debris monitoring unit, a computer determines whether individual monitored particles preferably impact one of the rotating panels or pass between the rotating panels. A control unit extends or retracts one or more booms which interconnect the sweeper core and the panels to change the moment of inertia of the sweeper and thereby the rotational velocity of the rotating panels. According to the method of the present invention, the change in panel rotational velocity increases the frequency of particles which desirably impact one of the panels and are thereby removed from orbit, while large particles which may damage the impact panels pass between the trailing edge of one panel and the leading edge of the rotationally succeeding panel.

Petro, Andrew J. (Inventor)

1991-01-01

362

Energy and the Elliptical Orbit  

ERIC Educational Resources Information Center

In the January 2007 issue of "The Physics Teacher," Prentis, Fulton, Hesse, and Mazzino describe a laboratory exercise in which students use a geometrical analysis inspired by Newton to show that an elliptical orbit and an inverse-square law force go hand in hand. The historical, geometrical, and teamwork aspects of the exercise are useful and…

Nettles, Bill

2009-01-01

363

Precision orbit computations for Starlette  

NASA Technical Reports Server (NTRS)

The Starlette satellite, launched in February 1975 by the French Centre National d'Etudes Spatiales, was designed to minimize the effects of nongravitational forces and to obtain the highest possible accuracy for laser range measurements. Analyses of the first four months of global laser tracking data confirmed the stability of the orbit and the precision to which the satellite's position is established.

Marsh, J. G.; Williamson, R. G.

1976-01-01

364

Aperture synthesis using orbiting telescopes  

NASA Technical Reports Server (NTRS)

A study was carried out to determine the feasibility, with current technology, of performing aperture synthesis using two telescopes orbiting the earth in coordinated orbits separated by approximately 10 m to 1 km. The objective was to determine whether there is a practical alternative to a very large, deployed, servo-controlled submillimeter telescope (i.e., the Large Deployable Reflector) for obtaining high-resolution submillimeter images of astronomical sources. It is found that suitable classes of orbits exist which can provide good UV coverage over the entire sky and the real-time correlation of wideband signals can be performed in orbit using current technology. The most difficult task appears to be the real-time determination of the orientation of the baseline vector in a stable coordinate system. A plausible scheme has been identified for the determination of an arbitrary direction to within 0.003 arcsec in an astrometric coordinate system. This scheme not only makes submillimeter interferometric image reconstruction possible but should also have numerous other applications.

Kuiper, T. B. H.; Synnott, S. P.; Linfield, R. P.; Resch, G. M.; Tubbs, E. F.

1985-01-01

365

The Earth Orbiting Space Debris  

Microsoft Academic Search

The space debris population is similar to the asteroid belt, since it is subject to a process of high-velocity mutual collisions that affects the long-term evolution of its size distribution. Presently, more than 10000 artificial debris particles with diameters larger than 10 cm (and more than 300000 with diameters larger than 1 cm) are orbiting the Earth, and are monitored

A. Rossi

2005-01-01

366

Getting a Crew into Orbit  

ERIC Educational Resources Information Center

Despite the temporary setback in our country's crewed space exploration program, there will continue to be missions requiring crews to orbit Earth and beyond. Under the NASA Authorization Act of 2010, NASA should have its own heavy launch rocket and crew vehicle developed by 2016. Private companies will continue to explore space, as well. At the…

Riddle, Bob

2011-01-01

367

Non-infectious orbital vasculitides  

PubMed Central

Non-infectious vasculitides comprise a large number of diseases. Many of these diseases can cause inflammation within the orbit and a clinical presentation, which mimics numerous other processes. Orbital disease can often be the initial presentation of a systemic process and early diagnosis can help prevent long-term, potentially fatal consequences. The evaluation and treatment of non-infectious orbital vasculitides are often complicated and require a thorough understanding of the disease and underlying systemic associations. The long-term prognosis visually and systemically must be weighed against the risks and benefits of the treatment regimen. A large variety of corticosteroid formulations currently exist and are the mainstay of initial treatment. Traditional steroid-sparing immunosuppressive agents are also an important arsenal against these vasculitides. Recently, a new class of drugs called biologics, which target the various mediators of the inflammation cascade, may potentially provide more effective and less toxic treatment. This review aims to synthesize the current literature on non-infectious orbital vasculitides. PMID:22361845

Perumal, B; Black, E H; Levin, F; Servat, J J

2012-01-01

368

Orbits in Strongly Curved Spacetime  

NSDL National Science Digital Library

This applet shows from three different physical perspectives the orbit of a low-mass test particle around a non-rotating black hole. Below the applet is an instructional guide to the applet and a description of the parameters involved.

Walker, John

369

Augmented orbiter heat rejection study  

NASA Technical Reports Server (NTRS)

Spacecraft radiator concepts are presented that relieve attitude restrictions required by the shuttle orbiter space radiator for baseline and extended capability STS missions. Cost effective heat rejection kits are considered which add additional capability in the form of attached spacelab radiators or a deployable radiator module.

Hixon, C. W.

1981-01-01

370

d Orbitals in an Octahedral Ligand Field  

NSDL National Science Digital Library

Here is a page that shows the d orbitals in an axis set. Running the mouse over an orbital reveals the "name" of that orbital. This is good practice for helping students link the name of an orbital to the orientation. This page is linked to an interactive 3-dimensional applet, similar to the one above, that shows the d orbitals in an octahedral ligand field. The user may also click on the name of any one of the d orbitals to obtain a larger 3-dimensional image. The images are rotatable and scalable.

371

Orbital Debris Research at NASA  

NASA Technical Reports Server (NTRS)

The United States has one of the most active programs of research of the orbital debris environment in the world. Much of the research is conducted by NASA s Orbital Debris Program Office at the Johnson Space Center. Past work by NASA has led to the development of national space policy which seeks to limit the growth of the debris population and limit the risk to spacecraft and humans in space and on the Earth from debris. NASA has also been instrumental in developing consistent international policies and standards. Much of NASA's efforts have been to measure and characterize the orbital debris population. The U.S. Department of Defense tracks and catalogs spacecraft and large debris with it's Space Surveillance Network while NASA concentrates on research on smaller debris. In low Earth orbit, NASA has utilized short wavelength radars such as Haystack, HAX, and Goldstone to statistically characterize the population in number, size, altitude, and inclination. For higher orbits, optical telescopes have been used. Much effort has gone into the understanding and removal of observational biases from both types of measurements. NASA is also striving to understand the material composition and shape characteristics of debris to assess these effects on the risk to operational spacecraft. All of these measurements along with data from ground tests provide the basis for near- and long-term modeling of the environment. NASA also develops tools used by spacecraft builders and operators to evaluate spacecraft and mission designs to assess compliance with debris standards and policies which limit the growth of the debris environment.

Stansbery, Eugene G.

2009-01-01

372

Space Shuttle Orbiter-Illustration  

NASA Technical Reports Server (NTRS)

This illustration is an orbiter cutaway view with callouts. The orbiter is both the brains and heart of the Space Transportation System (STS). About the same size and weight as a DC-9 aircraft, the orbiter contains the pressurized crew compartment (which can normally carry up to seven crew members), the huge cargo bay, and the three main engines mounted on its aft end. There are three levels to the crew cabin. Uppermost is the flight deck where the commander and the pilot control the mission. The middeck is where the gallery, toilet, sleep stations, and storage and experiment lockers are found for the basic needs of weightless daily living. Also located in the middeck is the airlock hatch into the cargo bay and space beyond. It is through this hatch and airlock that astronauts go to don their spacesuits and marned maneuvering units in preparation for extravehicular activities, more popularly known as spacewalks. The Space Shuttle's cargo bay is adaptable to hundreds of tasks. Large enough to accommodate a tour bus (60 x 15 feet or 18.3 x 4.6 meters), the cargo bay carries satellites, spacecraft, and spacelab scientific laboratories to and from Earth orbit. It is also a work station for astronauts to repair satellites, a foundation from which to erect space structures, and a hold for retrieved satellites to be returned to Earth. Thermal tile insulation and blankets (also known as the thermal protection system or TPS) cover the underbelly, bottom of the wings, and other heat-bearing surfaces of the orbiter to protect it during its fiery reentry into the Earth's atmosphere. The Shuttle's 24,000 individual tiles are made primarily of pure-sand silicate fibers, mixed with a ceramic binder. The solid rocket boosters (SRB's) are designed as an in-house Marshall Space Flight Center project, with United Space Boosters as the assembly and refurbishment contractor. The solid rocket motor (SRM) is provided by the Morton Thiokol Corporation.

2001-01-01

373

Conversion of Osculating Orbital Elements to Mean Orbital Elements  

NASA Technical Reports Server (NTRS)

Orbit determination and ephemeris generation or prediction over relatively long elapsed times can be accomplished with mean elements. The most simple and efficient method for orbit determination, which is also known as epoch point conversion, performs the conversion of osculating elements to mean elements by iterative procedures. Previous epoch point conversion methods are restricted to shorter elapsed times with linear convergence. The new method presented in this paper calculates an analytic initial guess of the unknown mean elements from a first order theory of secular perturbations and computes a transition matrix with accurate numerical partials. It thereby eliminates the problem of an inaccurate initial guess and an identity transition matrix employed by previous methods. With a good initial guess of the unknown mean elements and an accurate transition matrix, converging osculating elements to mean elements can be accomplished over long elapsed times with quadratic convergence.

Der, Gim J.; Danchick, Roy

1996-01-01

374

Prolate-Spheroidal Expansions of the Spin-Orbit, Spin-Spin, and Orbit-Orbit Operators  

Microsoft Academic Search

Prolate-spheroidal expansions of the spin-orbit, spin-spin, and orbit-orbit operators are derived. These expansions are analogs of the Neumann expansion for 1?r12 and can be used to study the corresponding exchange interactions in diatomic molecules.

R. L. Matcha; R. H. Pritchard; C. W. Kern

1971-01-01

375

Kepler's Orbit - Duration: 0:31.  

NASA Video Gallery

Kepler does not orbit the Earth, rather it orbits the Sun in concert with the Earth, slowly drifting away from Earth. Every 61 Earth years, Kepler and Earth will pass by each other. Throughout the ...

376

Current Status of Venus orbiter Akatsuki  

E-print Network

successfully reduced its weight by 65 kg. #12;Current status of Akatsuki (2) !!Orbit control maneuver using small thrusters For the rendezvous with Venus in 2015, Akatsuki has successfully performed orbit control

Widemann, Thomas

377

Close Proximity and Landing Orbits at Asteroids  

NASA Technical Reports Server (NTRS)

This paper discusses and describes the dynamics and control of a spacecraft orbiting close to or landing on an asteroid or comet. The paper presents analytical and numerical results which illustrate the challenges facing near-asteroid orbiters.

Scheeres, D. J.

1996-01-01

378

Analysing weak orbital signals in Gaia data  

NASA Astrophysics Data System (ADS)

Anomalous orbits are found when minimum-?2 estimation is applied to synthetic Gaia data for orbits with astrometric signatures comparable to the single-scan measurement error (Pourbaix 2002, A&A, 385, 686). These orbits are nearly parabolic, edge-on, and their major axes align with the line-of-sight to the observer. Such orbits violate the Copernican principle (CPr) and as such could be rejected. However, the preferred alternative is to develop a statistical technique that incorporates the CPr as a fundamental postulate. This can be achieved in a Bayesian context by defining a Copernican prior. Pourbaix's anomalous orbits then no longer arise. Instead, the selected orbits have a somewat higher ?2 but do not violate the CPr. The problem of detecting a weak additional orbit in an astrometric binary with a well-determined orbit is also treated.

Lucy, L. B.

2014-11-01

379

MOOSE: Manned On-Orbit Servicing Equipment  

NASA Technical Reports Server (NTRS)

The ability to service satellites has thus far been limited to low earth orbit platforms within reach of the Space Shuttle. Other orbits, such as geosynchronous orbits containing high-value spacecraft have not been attainable by a servicing vehicle. The useful life of a satellite can be extended by replacing spent propellant and damaged orbital replacement units, forestalling the need for eventual replacement. This growing need for satellite on-orbits servicing can be met by the Manned On-Orbit Servicing Equipment (MOOSE). Missions requiring orbit transfer capability, precision manipulation and maneuvering, and man-in-the-loop control can be accomplished using MOOSE. MOOSE is a flexible, reusable, single operator, aerobraking spacecraft designed to refuel, repair, and service orbiting spacecraft. MOOSE will be deployed from Space Station Freedom, (SSF), where it will be stored, resupplied, and refurbished.

Budinoff, J. (editor); Leontsinis, N. (editor); Lane, J. (editor); Singh, R. (editor); Angelone, K.; Boswell, C.; Chamberlain, I.; Concha, M.; Corrodo, M.; Custodio, O.

1993-01-01

380

Orbiter Kapton wire operational requirements and experience  

NASA Technical Reports Server (NTRS)

The agenda of this presentation includes the Orbiter wire selection requirements, the Orbiter wire usage, fabrication and test requirements, typical wiring installations, Kapton wire experience, NASA Kapton wire testing, summary, and backup data.

Peterson, R. V.

1994-01-01

381

Rational orbits around charged black holes  

SciTech Connect

We show that all eccentric timelike orbits in Reissner-Nordstroem spacetime can be classified using a taxonomy that draws upon an isomorphism between periodic orbits and the set of rational numbers. By virtue of the fact that the rationals are dense, the taxonomy can be used to approximate aperiodic orbits with periodic orbits. This may help reduce computational overhead for calculations in gravitational wave astronomy. Our dynamical systems approach enables us to study orbits for both charged and uncharged particles in spite of the fact that charged particle orbits around a charged black hole do not admit a simple one-dimensional effective potential description. Finally, we show that comparing periodic orbits in the Reissner-Nordstroem and Schwarzschild geometries enables us to distinguish charged and uncharged spacetimes by looking only at the orbital dynamics.

Misra, Vedant [Physics Department, Columbia University, New York, New York 10027 (United States); Levin, Janna [Department of Physics and Astronomy, Barnard College of Columbia University, 3009 Broadway, New York, New York 10027 (United States); Institute for Strings, Cosmology and Astroparticle Physics, Columbia University, New York, New York 10027 (United States)

2010-10-15

382

Orbits in the H2O molecule  

E-print Network

We study the forms of the orbits in a symmetric configuration of a realistic model of the H2O molecule with particular emphasis on the periodic orbits. We use an appropriate Poincar\\'e surface of section (PSS) and study the distribution of the orbits on this PSS for various energies. We find both ordered and chaotic orbits. The proportion of ordered orbits is almost 100% for small energies, but decreases abruptly beyond a critical energy. When the energy exceeds the escape energy there are still non-escaping orbits around stable periodic orbits. We study in detail the forms of the various periodic orbits, and their connections, by providing appropriate stability and bifurcation diagrams.

K. Efstathiou; G. Contopoulos

2001-02-07

383

Management of ocular, orbital, and adnexal trauma  

SciTech Connect

This book contains 20 chapters. Some of the chapter titles are: The Ruptured Globe: Primary Care; Corneal Trauma, Endophthalmitis; Antibiotic Usage; Radiology of Orbital Trauma; Maxillofacial Fractures; Orbital Infections; and Basic Management of Soft Tissue Injury.

Spoor, T.C.; Nesi, F.A.

1988-01-01

384

Nicholson et al.: Irregular Satellites of the Giant Planets 411 Irregular Satellites of the Giant Planets  

E-print Network

over 100, are likely to have been captured from heliocentric orbit during the early period of solar believed to have been captured from heliocentric orbit during the final phases of planetary accretion

Sheppard, Scott S.

385

Long-Term Observations of Stream Interaction Regions and Interplanetary Coronal Mass Ejections: Venus, Earth, and Jupiter Orbits  

NASA Astrophysics Data System (ADS)

Two types of large-scale solar wind structures, stream interaction regions (SIRs) and interplanetary coronal mass ejections (ICMEs), can drive interplanetary shocks, generate or accelerate energetic particles, and affect the planetary ionosphere and/or magnetosphere. To quantify the properties of SIRs and ICMEs at different heliocentric distances, we have identified and characterized these structures based on consistent criteria using the in situ plasma and magnetic field observations. The data sets used are Pioneer Venus Orbiter at 0.72 AU (1979 - 1988), Wind/ACE at 1 AU (1995 - 2006), and three Ulysses aphelion passes at 5.3 AU (partial 1992, 1997 - 1998, 2003 - 2005, representing slices at different phases of the solar cycle). The long-term observations enable us to study the solar cycle variations of these two structures. The parameters relevant to space weather modeling, such as the structure duration, width, maximum dynamic pressure, maximum magnetic field intensity, average speed, speed variation, and other properties of SIRs and ICMEs are all examined at each distance. ICMEs can generally affect the planetary environment more than SIRs at Venus and Earth, especially around solar maximum. However, when they propagate to 5.3 AU, some ICMEs and SIRs merge and form hybrid events at Jupiter. In general, SIRs have greater dynamic pressure, interaction strength and field intensity than ICMEs at Jupiter, and therefore they affect the space environment more than ICMEs there.

Jian, L. K.; Russell, C. T.; Luhmann, J. G.; Skoug, R. M.; Steinberg, J. T.

2009-04-01

386

Algorithms for orbit control on SPEAR  

SciTech Connect

A global orbit feedback system has been installed on SPEAR to help stabilize the position of the photon beams. The orbit control algorithms depend on either harmonic reconstruction of the orbit or eigenvector decomposition. The orbit motion is corrected by dipole corrector kicks determined from the inverse corrector-to-bpm response matrix. This paper outlines features of these control algorithms as applied to SPEAR.

Corbett, J.; Keeley, D.; Hettel, R.; Linscott, I.; Sebek, J. [Stanford Univ., CA (United States). Stanford Synchrotron Radiation Lab.

1994-06-01

387

An Analytical Satellite Orbit Predictor (ASOP)  

NASA Technical Reports Server (NTRS)

The documentation and user's guide are presented for the analytical satellite orbit predictor computer program which is intended to be used for computation of near-earth orbits including those of the shuttle orbiter and its payloads. The Poincare-Similar elements used make it possible to compute near-earth orbits to within an accuracy of a few meters. Recursive equations are used instead of complicated formulas. Execution time is on the order of a few milliseconds.

1979-01-01

388

Computer tools for optimizing orbit use  

Microsoft Academic Search

The ORBIT-II orbit-spacing-optimization program for GEO communications satellites is characterized and demonstrated. The problems inherent in current orbit-management (OM) techniques are discussed; the methods proposed to improve OM are surveyed (earth and satellite antenna characteristics, positioning flexibility, transmission efficiency, and interference criteria); and the possible administrative (WARC) approaches to OM are reviewed. The ORBIT-II program represents a tool capable of

T. Mizuno; Y. Ito; T. Muratani

1984-01-01

389

On-orbit spacecraft reliability  

NASA Technical Reports Server (NTRS)

Operational and historic data for 350 spacecraft from 52 U.S. space programs were analyzed for on-orbit reliability. Failure rates estimates are made for on-orbit operation of spacecraft subsystems, components, and piece parts, as well as estimates of failure probability for the same elements during launch. Confidence intervals for both parameters are also given. The results indicate that: (1) the success of spacecraft operation is only slightly affected by most reported incidents of anomalous behavior; (2) the occurrence of the majority of anomalous incidents could have been prevented piror to launch; (3) no detrimental effect of spacecraft dormancy is evident; (4) cycled components in general are not demonstrably less reliable than uncycled components; and (5) application of product assurance elements is conductive to spacecraft success.

Bloomquist, C.; Demars, D.; Graham, W.; Henmi, P.

1978-01-01

390

Polarization from an orbiting spot  

NASA Astrophysics Data System (ADS)

The polarization from a spot orbiting around Schwarzschild and extreme Kerr black holes is studied. We assume different models of local polarization. Firstly, as a toy model we set local polarization vector either normal to the disc plane, or we assume strictly azimuthal direction. Then we examine more realistic situation with a spot arising due to the emission from the primary source above the disc. We employ either Rayleigh single scattering or Compton multiple scattering approximations. Overall flux, degree and angle of polarization integrated over the whole orbit as well as their time dependence during the spot revolution are examined as functions of the observer's inclination angle. The gravitational and Doppler shifts, lensing effect as well as time delays are taken into account.

Dov?iak, Michal; Karas, Vladimír; Matt, Giorgio

2007-04-01

391

Analytic theory of orbit contraction  

NASA Technical Reports Server (NTRS)

The motion of a satellite in orbit, subject to atmospheric force and the motion of a reentry vehicle are governed by gravitational and aerodynamic forces. This suggests the derivation of a uniform set of equations applicable to both cases. For the case of satellite motion, by a proper transformation and by the method of averaging, a technique appropriate for long duration flight, the classical nonlinear differential equation describing the contraction of the major axis is derived. A rigorous analytic solution is used to integrate this equation with a high degree of accuracy, using Poincare's method of small parameters and Lagrange's expansion to explicitly express the major axis as a function of the eccentricity. The solution is uniformly valid for moderate and small eccentricities. For highly eccentric orbits, the asymptotic equation is derived directly from the general equation. Numerical solutions were generated to display the accuracy of the analytic theory.

Vinh, N. X.; Longuski, J. M.; Busemann, A.; Culp, R. D.

1977-01-01

392

Environmental dynamics at orbital altitudes  

NASA Technical Reports Server (NTRS)

The influence of real satellite aerodynamics on the determination of upper atmospheric density was investigated. A method of analysis of satellite drag data is presented which includes the effect of satellite lift and the variation in aerodynamic properties around the orbit. The studies indicate that satellite lift may be responsible for the observed orbit precession rather than a super rotation of the upper atmosphere. The influence of simplifying assumptions concerning the aerodynamics of objects in falling sphere analysis were evaluated and an improved method of analysis was developed. Wind tunnel data was used to develop more accurate drag coefficient relationships for studying altitudes between 80 and 120 Km. The improved drag coefficient relationships revealed a considerable error in previous falling sphere drag interpretation. These data were reanalyzed using the more accurate relationships. Theoretical investigations of the drag coefficient in the very low speed ratio region were also conducted.

Karr, G. R.

1976-01-01

393

Calculation of lunar orbit anomaly  

NASA Astrophysics Data System (ADS)

Studies of the Moon, with thanks to NASA and Johnson Space Center, have quantified an anomaly in measurements of lunar orbital evolution. This finding may have significance for cosmology and the speed of light. The Lunar Laser Ranging Experiment from Apollo reports the Moon's semimajor axis increasing at a rate of 3.82 +/- .07 cm/yr, anomalously high. Findings Sedimentary data indicates a rate of only 2.9 +/- 0.6 cm/yr. From historical eclipse records we can accurately calculate a rate of 2.82 +/- .08 cm/yr. A detailed numerical simulation of lunar orbital evolution predicts 2.91 cm/yr. LLRE's laser light differs from independent experiments by up to 12sigma.

Riofrio, Louise

2012-04-01

394

The Orbiting Primate Experiment (OPE)  

NASA Technical Reports Server (NTRS)

Instrumentation and life support systems are described for an experiment to determine the physiological effects of long term space flight on unrestrained, minimally instrumented rhesus macaques flown in orbit for periods up to six months or one year. On return from orbit, vestibular, cardiovascular, and skeletal muscle function will be tested. Blood chemistry and hematological studies will be conducted as well as tests of the immunological competence of selected animals. Nasal, rectal, and throat swabs will be used for bacterial and viral studies, and histopathological and histochemical investigations will be be made of all organs using light and electron microscopy. The experiment is being considered as a payload for the biomedical experiment scientific satellite.

Bourne, G. H.; Debourne, M. N. G.; Mcclure, H. M.

1977-01-01

395

Low thrust orbit determination program  

NASA Technical Reports Server (NTRS)

Logical flow and guidelines are provided for the construction of a low thrust orbit determination computer program. The program, tentatively called FRACAS (filter response analysis for continuously accelerating spacecraft), is capable of generating a reference low thrust trajectory, performing a linear covariance analysis of guidance and navigation processes, and analyzing trajectory nonlinearities in Monte Carlo fashion. The choice of trajectory, guidance and navigation models has been made after extensive literature surveys and investigation of previous software. A key part of program design relied upon experience gained in developing and using Martin Marietta Aerospace programs: TOPSEP (Targeting/Optimization for Solar Electric Propulsion), GODSEP (Guidance and Orbit Determination for SEP) and SIMSEP (Simulation of SEP).

Hong, P. E.; Shults, G. L.; Huling, K. R.; Ratliff, C. W.

1972-01-01

396

Geopotential resonances on Vanguard orbits  

NASA Technical Reports Server (NTRS)

Since their establishment in 1959 the orbits of Vanguard 3 (1959-7A) and the Vanguard 2 rocket (1959-2B) have been slowly contracting through at least five strong resonances of eleventh order. Tracking with Baker-Nunn cameras and the U.S. Navy space surveillance (radio interferometer) system over a 14-year period has revealed resonant fluctuations on them of up to 0.035 deg in inclination (peak to peak). Six geopotential terms (lumped coefficients) of eleventh order and three of twenty-second order have been measured by using orbit inclinations derived from this tracking record. The terms of eleventh order are significantly smaller than is predicted by Kaula's rule. (The lumped coefficients are sensitive to geopotential effects as high as thirty-seventh degree.) These observed terms are compatible with a recent 27-satellite geopotential solution (GEM 7) whose formal coefficent errors are increased by a factor of 3.3.

Wagner, C. A.

1977-01-01

397

Has Nemesis' orbit been detected?  

NASA Technical Reports Server (NTRS)

The orbital angular momenta of 126 very young comets are calculated from the orbital data of Marsden and Roemer (1982) and analyzed statistically. A large anisotropy is detected in a plane almost perpendicular to the ecliptic and shown to have a characteristic dissipation lifetime of 10-30 Myr. Dynamic evolution computations indicate that the impulse which produced the anisotropy is that of a very slow massive (10-90 Jupiter mass) body, which is bound to the solar system, passed its 15,000-35,000-AU perihelion about 2-15 Myr ago, and has period 5-50 Myr. It is suggested that this body could well be identical to Nemesis, the object proposed to explain mass faunal extinctions.

Delsemme, A. H.

1986-01-01

398

Some Observations on Molecular Orbital Theory  

ERIC Educational Resources Information Center

A few flawed predictions in the context of homonuclear diatomic molecules are presented in order to introduce students to molecular orbital (MO) theory. A common misrepresentation of the relationship between the energy of an atomic orbital and the energy of the MO associated with the atomic orbital is illustrated.

Journal of Chemical Education, 2005

2005-01-01

399

The geostationary orbit and developing countries  

NASA Technical Reports Server (NTRS)

The geostationary orbit is becoming congested due to use by several countries throughout the world, and the request for use of this orbit is increasing. There are 188 geostationary stations in operation. An equitable distribution of stations on this orbit is requested.

Medina, E. R.

1982-01-01

400

Orbit Transfer Trajectory Optimization With Electric Engine  

Microsoft Academic Search

In this paper, it is studied optimal coplanar orbit transfer of a satellite from a low Earth orbit to a low Earth orbit using electric propulsion system. In this case the satellite is passing through the shadow area of the Earth. During this time, supplying electric power to the satellite is going to be difficult due to the solar array

Dong-Hyun Cho; Dong-hun Lee; Min-Jae Tahk

2006-01-01

401

ORBIT CONTROL FOR THE CANADIAN LIGHT SOURCE  

Microsoft Academic Search

Abstract The orbit control system for the Canadian Light Source storage ring is designed to provide both static global orbit correction and active correction up to 100 Hz. The system ismade up of 48 button monitors (X and Y), 24 fast corrector magnets (X and Y), and 24 static correction coils in sextupole ,magnets ,(X and Y). The static orbit

R. Berg; L. Dallin; J. M. Vogt

2004-01-01

402

Orbit Control at the SLS Storage Ring  

Microsoft Academic Search

Precise orbit control is one of the crucial ingredients for stable operation of the SLS storage ring. The orbits are taken by the digital BPM system which allows beam po- sition measurements to the sub-micron level at sampling rates of up to 4 kHz at 72 locations in the ring. Orbits are corrected with respect to a user defined reference

T. Schilcher; M. Böge; J. Chrin; P. Pollet; V. Schlott

2003-01-01

403

Navigation of Spacecraft in Unstable Orbital Environments  

Microsoft Academic Search

The novelty of libration point orbits is their hyperbolic instability. It is this basic property that allows them to serve as connections between disparate regions of space, and gives them their many practical uses. This same property also makes the navigation of spacecraft in libration point orbits a fascinating subject, one which exposes new questions in orbit determination and control.

D. J. Scheeres

404

SPECIAL NATURE OF ORBITAL ANGULAR MOMENTUM  

Microsoft Academic Search

The properties of orbital angular momentam operators are examined within ; the framework of the formal theory of angular momentum. It is demonstrated that ; the occurrence of only integral quantum numbers in the orbital theory is a ; consequence of the particular form of the orbital operators. Single-valuedness ; of the eigenfunctions need not be postulated. (auth);

James D. Louck

1963-01-01

405

What is Orbital Angular Matthias Burkardt  

E-print Network

What is Orbital Angular Momentum? Matthias Burkardt burkardt@nmsu.edu New Mexico State University What is Orbital Angular Momentum? ­ p.1/22 #12;Motivation polarized DIS: only 30% of the proton spin = 1 quest for the remaining 70% quark orbital angular momentum (OAM) gluon spin gluon OAM How

406

The Meaning of d-Orbital Labels  

ERIC Educational Resources Information Center

The orbital labels when considered as the angular part of the wavefunction can serve as an inclusive principle, which the students can use to construct the spatial shapes of the d orbitals from their labels. The spatial orientation of the different d orbitals guides the crystal field theory which includes d(sub xy), d(sub yz) and d(sub xz) lying…

Ashkenazi, Guy

2005-01-01

407

Probes of Orbital Angular Matthias Burkardt  

E-print Network

Probes of Orbital Angular Momentum Matthias Burkardt burkardt@nmsu.edu New Mexico State University Las Cruces, NM, 88003, U.S.A. Probes of Orbital Angular Momentum ­ p.1/40 #12;Motivation Decomposition carry the nucleon spin? Probes of Orbital Angular Momentum ­ p.2/40 #12;Outline The anomalous magnetic

408

Localized correlation treatment using natural bond orbitals  

Microsoft Academic Search

We present studies using natural bond orbitals (NBOs) as a starting point for a localized electron correlation treatment, as these kind of localized orbitals lead to CCSD results which show significant transferability and exponential decay patterns in the T?2 amplitudes. The NBO CCSD approach combines the advantages of both the HF CCSD formulation (less amplitudes, orthogonal orbitals) and the AO-based

N. Flocke; Rodney J. Bartlett

2003-01-01

409

Prototyping a Planning System for Orbital Reconstruction  

E-print Network

. A malformed orbit causes one eye to be displaced from a position that is sym- metrical to the eyePrototyping a Planning System for Orbital Reconstruction Jan Fischer1 , Melissa Mekic1 , ´Angel del orbit to be symmetrical to the intact one. Here, the main difficulty of this intervention

Bartz, Dirk

410

Mars Climate Orbiter Mishap Investigation Board  

E-print Network

Mars Climate Orbiter Mishap Investigation Board Phase I Report November 10, 1999 #12;2 Table of Contents Mars Climate Orbiter Mishap Investigation Board Phase I Report Page Signature Page (Board Members) 3 List of Consultants 4 Acknowledgements 5 Executive Summary 6 1. Mars Climate Orbiter (MCO

Leveson, Nancy

411

Outgassing products from orbiter TPS materials  

NASA Technical Reports Server (NTRS)

The Space Transportation System (STS) orbiters are known to be significant sources of outgassing in low earth orbit (LEO). Infrared and mass spectra of residues and outgassing from orbiter thermal protection tile and an external blanket are presented. Several sources of methyl and phenyl methyl silicones are identified. About fifty pounds of silicones are estimated to be outgassed during an STS mission.

Harvey, Gale A.; Lash, Tom J.; Rawls, J. Richard

1995-01-01

412

N-observations and radar orbits  

NASA Astrophysics Data System (ADS)

Initial asteriod orbits are determined by a least squares adjustment of an arbitrary number (N) of optical and radar observations. The usual separation, into an orbit determination by three observations and a subsequent differential orbit improvement, is combined into a single algorithm. A priori information is used for very small arcs. Ephemerides very suitable for linking are obtained by strictly linear computations.

Kristensen, Leif Kahl

2007-07-01

413

Conversion Between Osculating and Mean Orbital Elements  

NASA Technical Reports Server (NTRS)

Osculating/Mean Orbital Element Conversion (C version) (OSMEANC) is a C-language computer program that performs precise conversions between osculating and mean classical orbital elements. OSMEANC can be used for precise design of spacecraft missions and maneuvers and precise calculation of planetary orbits. The program accounts for the full complexity of gravitational fields, including aspherical and third-body effects.

Guinn, Joseph; Chung, Min-Kun; Vincent, Mark

2006-01-01

414

Model orbits of asteroid 3040 Kozai  

Microsoft Academic Search

The orbital evolutions of the asteroid 3040 Kozai and model asteroids with similar orbits have been investigated. Their osculating orbits for an epoch 1991 December 10 were numerically integrated forward within the interval of 20,000 years, using a dynamical model of the solar system consisting of all inner planets, Jupiter, and Saturn.

Nina A. Solovaya; Eduard M. Pittich

1995-01-01

415

Assessing the Risk of Orbital Debris Impact  

Microsoft Academic Search

A Space Debris Impact Risk Analysis Tool (SDIRAT) was developed and implemented to assess the orbital debris impact risk on a specified target in Earth orbit, in terms of flux, relative velocity, impact velocity, direction of the incoming particles, debris mass and diameter. Based on a deterministic approach, SDIRAT uses a realistic orbital debris population where each representative particle is

C. Pardini; L. Anselmo

1999-01-01

416

Orbital-Transfer Vehicle With Aerodynamic Braking  

NASA Technical Reports Server (NTRS)

Vehicle includes airbrake for deceleration into lower orbit. Report describes vehicle for carrying payloads between low and high orbits around Earth. Vehicle uses thin, upper atmosphere for braking when returning to low orbit. Since less propellant needed than required for full retrorocket braking, vehicle carries larger payload and therefore reduces cost of space transportation.

Scott, C. D.; Nagy, K.; Roberts, B. B.; Ried, R. C.; Kroll, K.; Gamble, J.

1986-01-01

417

Orbital magnetoelectric response of insulating crystals  

Microsoft Academic Search

We calculate the orbital magnetoelectric polarizability (OMP) of a periodic insulator as the linear orbital magnetization response to a homogeneous electric field. We begin by considering the orbital magnetization (OM) in a finite field, and find that it can be written as a sum of three terms, one of which has no counterpart at zero field. The extra contribution is

Andrei Malashevich; Ivo Souza; Sinisa Coh; David Vanderbilt

2010-01-01

418

Life expectancy following orbital exenteration.  

PubMed

Orbital exenteration is a physically debilitating procedure that may be a necessity in the management of orbital malignancy. It requires a sensitive multidisciplinary approach, both preoperatively and postoperatively. Providing life expectancy information for patients during preoperative counselling is pertinent to informed consent and in addressing patients' expectations. A retrospective review from one tertiary care centre was undertaken for a cohort of patients who were exenterated for orbital malignancy between 1998 and 2010. The cases were identified using an International Classification of Diseases 10th Revision (ICD-10)-derived database and were analysed using Prism statistical software (V.5.04). Cause of death was ascertained by liaising with the general practitioner and the National Registrar Office for Births, Deaths, and Marriages, Southport, UK. In total, 41 men and 32 women were identified. Mean age was 72?years with 47 cases living and 26 deceased at the time of review. The overall 5-year survival rate in this study was 64%. Kaplan-Meier analysis for basal cell carcinoma (BCC) against non-BCC returned a p value of 0.0199, with an HR of 0.3927 (CI 0.1788 to 0.8626). Kaplan-Meier analysis for cleared against non-cleared margins returned a p value of 0.2890, with an HR of 0.6571(CI 0.3024 to 1.428). Our results represent the highest 5-year survival data to date. However, the overall prognosis for patients who undergo orbital exenteration for malignancy remains poor. We hypothesise that the causes are multi-factorial. We recommend a multidisciplinary approach to the care of these patients, involving head and neck teams, oncology and other appropriate specialties, to optimise outcomes for this vulnerable patient group. PMID:24879806

Wong, James Chiun Lon; Thampy, Reshma; Cook, Anne

2015-01-01

419

Ancient schwannoma of the orbit  

PubMed Central

The ancient schwannoma is a rare variant of a neurilemoma with a course typical of a slow-growing benign neoplasm. Histologically, it can be confused with a malignant mesenchymal tumor because of increased cellularity, nuclear pleomorphism, and hyperchromatism. Despite the degree of nuclear atypia, mitotic figures are absent. We describe the clinical and histopathologic features of an ancient schwannoma of the orbit. A need for early removal of such tumors is recommended to prevent complications. PMID:25136229

Kulkarni, Anjali S.; Anjum, Shaziya; Kokandakar, Hemant R.; Bindu, Rajan S.; Awargaonkar, Amarnath

2014-01-01

420

The Orbit of the Moon  

NSDL National Science Digital Library

Martin Hackworth of Idaho State University has created this lab activity to help students measure the eccentricity of the moon's orbit. Students will need a drafting compass, protractor, vernier caliper, and a personal computer with a spreadsheet application. The lesson plan features an objective, needed equipment, general discussion, and procedure . In addition, the lesson concludes with six questions to test a student's overall knowledge of this lesson. The resource is provided as a pdf.

Hackworth, Martin

421

Comet Orbits: Prediction, Nongravitational Effects  

NASA Technical Reports Server (NTRS)

The problems of calculating cometary orbits are discussed, with particular attention to that of predicting the returns of periodic comets. It is shown that the only inherent difficulty arises from the action of nongravitational forces. Recent progress toward an understanding of these forces is described in detail, both from the point of view of fitting the observations and of interpreting the forces in terms of the Whipple icy-conglomerate model.

Marsden, B. G.

1972-01-01

422

Orbital Space Plane (OSP) Program  

NASA Technical Reports Server (NTRS)

Lockheed Martin has been an active participant in NASA's Space Launch Initiative (SLI) programs over the past several years. SLI, part of NASA's Integrated Space Transportation Plan (ISTP), was restructured in November of 2002 to focus the overall theme of safer, more afford-able space transportation along two paths - the Orbital Space Plane Program and the Next Generation Launch Technology programs. The Orbital Space Plane Program has the goal of providing rescue capability from the International Space Station by 2008 and transfer capability for crew (and limited cargo) by 2012. The Next Generation Launch Technology program is combining research and development efforts from the 2nd Generation Reusable Launch Vehicle (2GRLV) program with cutting-edge, advanced space transportation programs (previously designated 3rd Generation) into one program aimed at enabling safe, reliable, cost-effective reusable launch systems by the middle of the next decade. Lockheed Martin is one of three prime contractors working to bring Orbital Space Plane system concepts to a system definition level of maturity by December of 2003. This paper and presentation will update the international community on the progress of the' OSP program, from an industry perspective, and provide insights into Lockheed Martin's role in enabling the vision of a safer, more affordable means of taking people to and from space.

McKenzie, Patrick M.

2003-01-01

423

Density-orbital embedding theory  

SciTech Connect

In the article density-orbital embedding (DOE) theory is proposed. DOE is based on the concept of density orbital (DO), which is a generalization of the square root of the density for real functions and fractional electron numbers. The basic feature of DOE is the representation of the total supermolecular density {rho}{sub s} as the square of the sum of the DO {phi}{sub a}, which represents the active subsystem A and the square root of the frozen density {rho}{sub f} of the environment F. The correct {rho}{sub s} is obtained with {phi}{sub a} being negative in the regions in which {rho}{sub f} might exceed {rho}{sub s}. This makes it possible to obtain the correct {rho}{sub s} with a broad range of the input frozen densities {rho}{sub f} so that DOE resolves the problem of the frozen-density admissibility of the current frozen-density embedding theory. The DOE Euler equation for the DO {phi}{sub a} is derived with the characteristic embedding potential representing the effect of the environment. The DO square {phi}{sub a}{sup 2} is determined from the orbitals of the effective Kohn-Sham (KS) system. Self-consistent solution of the corresponding one-electron KS equations yields not only {phi}{sub a}{sup 2}, but also the DO {phi}{sub a} itself.

Gritsenko, O. V.; Visscher, L. [Section Theoretical Chemistry, VU University, De Boelelaan 1083, NL-1081 HV Amsterdam (Netherlands) and Pohang University of Science and Technology, Pohang (Korea, Republic of)

2010-09-15

424

Idiopathic Orbital Inflammation Syndrome with Retro-Orbital Involvement: A Retrospective Study of Eight Patients  

PubMed Central

Background The aim of this retrospective study was to document the clinical findings and radiological features of idiopathic orbital inflammation syndrome with retro-orbital involvement. Methods We searched for ophthalmological patients who received orbital imaging at Zhejiang Provincial People's Hospital between October 2003 and April 2010. Seventy-three patients were diagnosed with idiopathic orbital inflammation syndrome based on clinicoradiological features, with pathological confirmation of nonspecific inflammatory conditions in 47 patients. Eight patients (11%) had MRI or CT evidence of retro-orbital involvement. All 8 patients were diagnosed with idiopathic orbital inflammation syndrome after biopsy of the orbital lesion. MR images were obtained for all 8 patients; 3 patients also had a contrast-enhanced CT scan. Results Seven out of 8 patients with retro-orbital involvement also had orbital apex lesions. Of the 65 patients without retro-orbital involvement, 19 had orbital apex lesions. The difference in the number of patients with orbital apex lesions between the two populations was significant (Fisher exact test P?=?.002). In all 8 patients with retro-orbital involvement, the inflammation spread through the superior orbital fissure. The retro-orbital lesions were isointense to grey matter on T1-weighted images, hypointense on T2-weighted images, and displayed uniform contrast enhancement; on contrast-enhanced CT scans, they were hyperdense relative to the contralateral mirror area and had radiological contours that were similar to those seen on MR images. The diffuse inflammation with marked sclerosis and hyalinization that we observed in the patients with retro-orbital involvement is consistent with the diagnosis of the sclerosing subtype of idiopathic orbital inflammation syndrome. All 8 patients also complained of mild to moderate periorbital pain (headache). Conclusions In patients with idiopathic orbital inflammation syndrome, it is important to perform MRI and CT scans to identify possible retro-orbital involvement. Retro-orbital involvement is more frequent when the lesion is present in the orbital apex. PMID:23437329

Li, Yumei; Lip, Gerald; Chong, Vincent; Yuan, Jianhua; Ding, Zhongxiang

2013-01-01

425

A universal on-orbit servicing system used in the geostationary orbit  

Microsoft Academic Search

The geostationary orbit (GEO), a unique satellite orbit of the human beings, is a very precious orbit resource. However, the continuous increasing of GEO debris makes the GEO orbit more and more crowded. Moreover, the failures of GEO spacecrafts will result in large economic cost and other bad impacts. In this paper, we proposed a space robotic servicing system, and

Wenfu Xu; Bin Liang; Bing Li; Yangsheng Xu

2011-01-01

426

Examination of a constrained three-impulse trajectory between low planetary orbits and circulating orbits  

Microsoft Academic Search

Circulating orbits have been investigated to provide regular periodic transfers between the Earth and Mars. The circulating orbits pass close enough to each planet to be considered hyperbolic in planetocentric frame. The large spacecraft in the circulating orbit is resupplied by a smaller 'Taxi' spacecraft leaving a low planetary orbit. The Taxi follows a three-impulse patched-conic trajectory to travel from

Andrew J. Knoedler

1992-01-01

427

Understanding glycine conformation through molecular orbitals  

NASA Astrophysics Data System (ADS)

The four most stable Cs conformers of glycine have been investigated using a variety of quantum-mechanical methods based on Hartree-Fock theory, density-functional theory (B3LYP and statistical average of orbital potential), and electron propagation (OVGF) treatments. Information obtained from these models were analyzed in coordinate and momentum spaces using dual space analysis to provide insight based on orbitals into the bonding mechanisms of glycine conformers, which are generated by rotation of C-O(H) (II), C-C (III), and C-N (IV) bonds from the global minimum structure (I). Wave functions generated from the B3LYP/TZVP model revealed that each rotation produced a unique set of fingerprint orbitals that correspond to a specific group of outer valence orbitals, generally of a' symmetry. Orbitals 14a', 13a', 12a', and 11a' are identified as the fingerprint orbitals for the C-O(H) (II) rotation, whereas fingerprint orbitals for the C-C (III) bond rotation are located as 16a' [highest occupied molecular orbital (HOMO)], 15a' [next highest molecular occupied molecular orbital (NHOMO)], 14a', and 12a' orbitals. Fingerprint orbitals for IV generated by the combined rotations around the C-C, C-O(H), and C-N bonds are found as 16a', 15a', 14a', 13a', and 11a', as well as in orbitals 2a? and 1a?. Orbital 14a' is identified as the fingerprint orbital for all three conformational processes, as it is the only orbital in the outer valence region which is significantly affected by the conformational processes regardless rotation of which bond. Binding energies, molecular geometries, and other molecular properties such as dipole moments calculated based on the specified treatments agree well with available experimental measurements and with previous theoretical calculation.

Falzon, Chantal T.; Wang, Feng

2005-12-01

428

The orbital record in stratigraphy  

NASA Astrophysics Data System (ADS)

Orbital signals are being discovered in pre-Pleistocene sediments. Due to their hierarchical nature these cycle patterns are complex, and the imprecision of geochronology generally makes the assignment of stratigraphic cycles to specific orbital cycles uncertain, but in sequences such as the limnic Newark Group under study by Olsen and pelagic Cretaceous sequence worked on by our Italo-American group the relative frequencies yield a definitive match to the Milankovitch hierarchy. Due to the multiple ways in which climate impinges on depositional systems, the orbital signals are recorded in a multiplicity of parameters, and affect different sedimentary facies in different ways. In platform carbonates, for example, the chief effect is via sea-level variations (possibly tied to fluctuating ice volume), resulting in cycles of emergence and submergence. In limnic systems it finds its most dramatic expression in alternations of lake and playa conditions. Biogenic pelagic oozes such as chalks and the limestones derived from them display variations in the carbonate supplied by planktonic organisms such as coccolithophores and foraminifera, and also record variations in the aeration of bottom waters. Whereas early studies of stratigraphic cyclicity relied mainly on bedding variations visible in the field, present studies are supplementing these with instrumental scans of geochemical, paleontological, and geophysical parameters which yield quantitative curves amenable to time-series analysis; such analysis is, however, limited by problems of distorted time-scales. My own work has been largely concentrated on pelagic systems. In these, the sensitivity of pelagic organisms to climatic-oceanic changes, combined with the sensitivity of botton life to changes in oxygen availability (commonly much more restricted in the Past than now) has left cyclic patterns related to orbital forcing. These systems are further attractive because (1) they tend to offer depositional continuity, and (2) presence of abundant microfossils yields close ties to geochronology. A tantalizing possibility that stratigraphy may yield a record of orbital signals unrelated to climate has turned up in magnetic studies of our Cretaceous core. Magnetic secular variations here carry a strong 39 ka periodicity, corresponding to the theoretical obliquity period of that time - Does the obliquity cycle perhaps have some direct influence on the magnetic field?

Fischer, Alfred G.

1992-12-01

429

The orbital record in stratigraphy  

NASA Technical Reports Server (NTRS)

Orbital signals are being discovered in pre-Pleistocene sediments. Due to their hierarchical nature these cycle patterns are complex, and the imprecision of geochronology generally makes the assignment of stratigraphic cycles to specific orbital cycles uncertain, but in sequences such as the limnic Newark Group under study by Olsen and pelagic Cretaceous sequence worked on by our Italo-American group the relative frequencies yield a definitive match to the Milankovitch hierarchy. Due to the multiple ways in which climate impinges on depositional systems, the orbital signals are recorded in a multiplicity of parameters, and affect different sedimentary facies in different ways. In platform carbonates, for example, the chief effect is via sea-level variations (possibly tied to fluctuating ice volume), resulting in cycles of emergence and submergence. In limnic systems it finds its most dramatic expression in alternations of lake and playa conditions. Biogenic pelagic oozes such as chalks and the limestones derived from them display variations in the carbonate supplied by planktonic organisms such as coccolithophores and foraminifera, and also record variations in the aeration of bottom waters. Whereas early studies of stratigraphic cyclicity relied mainly on bedding variations visible in the field, present studies are supplementing these with instrumental scans of geochemical, paleontological, and geophysical parameters which yield quantitative curves amenable to time-series analysis; such analysis is, however, limited by problems of distorted time-scales. My own work has been largely concentrated on pelagic systems. In these, the sensitivity of pelagic organisms to climatic-oceanic changes, combined with the sensitivity of botton life to changes in oxygen availability (commonly much more restricted in the Past than now) has left cyclic patterns related to orbital forcing. These systems are further attractive because (1) they tend to offer depositional continuity, and (2) presence of abundant microfossils yields close ties to geochronology. A tantalizing possibility that stratigraphy may yield a record of orbital signals unrelated to climate has turned up in magnetic studies of our Cretaceous core. Magnetic secular variations here carry a strong 39 ka periodicity, corresponding to the theoretical obliquity period of that time - Does the obliquity cycle perhaps have some direct influence on the magnetic field?

Fischer, Alfred G.

1992-01-01

430

On-orbit flight control algorithm description  

NASA Technical Reports Server (NTRS)

Algorithms are presented for rotational and translational control of the space shuttle orbiter in the orbital mission phases, which are external tank separation, orbit insertion, on-orbit and de-orbit. The program provides a versatile control system structure while maintaining uniform communications with other programs, sensors, and control effectors by using an executive routine/functional subroutine format. Software functional requirements are described using block diagrams where feasible, and input--output tables, and the software implementation of each function is presented in equations and structured flow charts. Included are a glossary of all symbols used to define the requirements, and an appendix of supportive material.

1975-01-01

431

Circular orbits on a warped spandex fabric  

E-print Network

We present a theoretical and experimental analysis of circular-like orbits made by a marble rolling on a warped spandex fabric. We show that the mass of the fabric interior to the orbital path influences the motion of the marble in a nontrivial way, and can even dominate the orbital characteristics. We also compare a Kepler-like expression for such orbits to similar expressions for orbits about a spherically-symmetric massive object in the presence of a constant vacuum energy, as described by general relativity.

Chad A. Middleton; Michael Langston

2013-12-10

432

Circular orbits on a warped spandex fabric  

NASA Astrophysics Data System (ADS)

We present a theoretical and experimental analysis of circular-like orbits made by a marble rolling on a warped spandex fabric. We show that the mass of the fabric interior to the orbital path influences the motion of the marble in a nontrivial way and can even dominate the orbital characteristics. We also compare a Kepler-like expression for such orbits to similar expressions for orbits about a spherically symmetric massive object in the presence of a constant vacuum energy, as described by general relativity.

Middleton, Chad A.; Langston, Michael

2014-04-01

433

A Southern Hemisphere radar meteor orbit survey  

NASA Technical Reports Server (NTRS)

A meteor radar system has been operated on a routine basis near Christchurch, New Zealand, to determine the orbits of Earth-impacting interplanetary dust and meteoroids. The system sensitivity is +13 visual magnitude, corresponding to approximately 100 micron sized meteoroids. With an orbital precision of 2 degrees in angular elements and 10 percent in orbital energy (1/a), the operation yields an average of 1500 orbits daily with a total to date in excess of 10(exp 5). The use of pc's and automated data reduction permit the large orbital data sets we collect to be routinely reduced. Some illustrative examples are presented of the signal formats/processing and the results of data reduction, giving the individual orbital elements and hence the overall distributions. Current studies include the distribution of dust in the inner solar system; the influx of meteoroids associated with near-Earth asteroids; and the orbital structure existing in comet-produced streams.

Baggaley, W. Jack; Steel, Duncan I.; Taylor, Andrew D.

1992-01-01

434

Orbital inflammatory disease in relapsing polychondritis.  

PubMed

We present a 73-year-old Chinese male with bilateral relapsing, remitting orbital inflammatory disease associated with relapsing polychondritis. He first presented with right orbital inflammation that did not improve despite antibiotic treatment. Computer tomography (CT) of the orbits showed a soft tissue mass along the roof of the orbit, which was biopsied, revealing acute on chronic inflammation. There was complete resolution of his orbital inflammation within 2 weeks of initiating systemic steroid treatment. He subsequently developed recurrent bouts of left orbital inflammation. One year later, he was diagnosed with relapsing polychondritis and subsequently developed multiple myeloma seven years later. Comanagement with a rheumatologist will be helpful to achieve control of the disease with judicious use of immunosuppression. Long-term follow-up of the patient will be necessary to monitor for malignant transformation of the orbital lesion, as well as the development of other hematologic malignancies. PMID:24831308

Teo, Livia; Choo, Chai Teck

2014-08-01

435

Pioneer probe mission with orbiter option  

NASA Technical Reports Server (NTRS)

A spacecraft is described which is based on Pioneer 10 and 11, and existing propulsion technology; it can transport and release a probe for entry into Jupiter's atmosphere, and subsequently maneuver to place the spacecraft in orbit about Jupiter. Orbital operations last 3 years and include maneuvers to provide multiple close satellite encounters which allow the orbit to be significantly changed to explore different parts of the magnetosphere. A mission summary, a guide to related documents, and background information about Jupiter are presented along with mission analysis over the complete mission profile. Other topics discussed include the launch, interplanetary flight, probe release and orbit deflection, probe entry, orbit selection, orbit insertion, periapsis raising, spacecraft description, and the effects of Jupiter's radiation belt on both orbiter and the probe.

1975-01-01

436

Long-term Observations of Stream Interaction Regions and Interplanetary Coronal Mass Ejections at Venus, Earth, and Jupiter Orbits  

NASA Astrophysics Data System (ADS)

Two types of large-scale structures occur in the solar wind, stream interaction regions (SIRs) and interplanetary coronal mass ejections (ICMEs). To study their radial evolution and solar cycle variation, we have identified and characterized SIRs and ICMEs based on consistent criteria using magnetic field and plasma observations. The data sets used are Pioneer Venus Orbiter at 0.72 AU (1979 - 1988), Wind/ACE at 1 AU (1995 - 2006), and 3 Ulysses aphelion passes at 5.3 AU (partial 1992, 1997 - 1998, 2003 - 2005, representing slices at different phases of the solar cycle). From the statistical analysis of these long-term observations, we find the SIR occurrence rate has but a weak solar cycle dependence, while the ICME occurrence rate follows the solar cycle. The shock association rates of both SIRs and ICMEs roughly follow the solar cycle. The fraction of ICMEs that are like magnetic clouds declines with solar activity. Structure width, maximum magnetic field intensity, maximum total perpendicular pressure (the sum of magnetic pressure and perpendicular plasma thermal pressure), velocity variation, and other properties of SIRs and ICMEs are also examined. The same solar-cycle variations are found at both 0.72 and 1 AU. The fraction of SIRs occurring with shocks increases with heliocentric distance, with about 26% of SIRs at 1 AU occurring with shocks. SIRs and ICMEs merge as they propagate to 5.3 AU, resulting in many hybrid events at Jupiter orbit. SIRs have greater dynamic pressure, interaction strength and field intensity at 5.3 AU than ICMEs.

Jian, Lan; Russell, Christopher; Luhmann, Janet G.; Skoug, Ruth; Steinberg, John

437

Orbital tumors: operative and therapeutic strategies.  

PubMed

The term "orbital tumors" includes diverse benign or malignant space-occupying lesions of the orbit, often leading to dystopia of the eyeball, motility disturbances, diplopia, visual field defects, and sometimes a complete loss of vision. Removing these tumors in a limited surgical field is challenging. Therefore, the preservation of function is a primary concern. We retrospectively reviewed 671 patients with orbital tumors from October 1999 to June 2014. Diagnosis on referral, presenting symptoms, radiological records, histology of the primary tumor or orbital metastasis, and treatment choice were analyzed. Among the 671 orbital tumors, 40% were accessed anteriorly, 36% via an orbitotomy with temporary osteotomy, and 23.9% underwent an orbital exenteration. As an illustration of the operative strategies with subsequent reconstructions, a distinction was made among the main indication groups: (1) function-preserving therapy for retrobulbar tumors, (2) malignant tumors of the conjunctiva and the eyelids, (3) exenteration of the orbit and subsequent reconstruction, and (4) operative and therapeutic strategy for orbital metastases. Adequate preoperative use of modern imaging techniques and thorough planning of the operation are crucial. Accurate histopathological diagnosis is crucial for planning appropriate therapeutic and surgical interventions. New innovative treatment concepts and surgical techniques arise from the close cooperation of related disciplines such as ophthalmology and neurosurgery. Although an orbital exenteration in patients with eyelid and conjunctival carcinomas can now often be avoided, eye-preserving treatment for locally advanced carcinomas of the conjunctiva and eyelid must be attempted. For extensive orbital malignancies, orbital exenteration is curative. In this context, primary closure of the orbit can improve the patient's quality of life and avoid subsequent complications. Concerning orbital metastasis, early diagnosis can preserve function and fulfil the esthetic demands of the patients. In palliative tumor disease, operative procedures such as orbital decompression or tumor debulking can reduce patient complaints and contribute to improved quality of life. PMID:25397713

Pförtner, R; Mohr, C; Daamen, J; Metz, A

2014-10-01

438

Colors of dynamically associated asteroid pairs Nicholas A. Moskovitz  

E-print Network

studies have identified pairs of asteroids that reside in nearly identical heliocentric orbits. Possible asteroids have revealed over 80 pairs of asteroids that reside in nearly iden- tical heliocentric orbits. Backwards integration of these pairs' heliocentric orbits sug- gests they may have separated recently

Moskovitz, Nicholas

439

Kalman Orbit Optimized Loop Tracking  

NASA Technical Reports Server (NTRS)

Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.

Young, Lawrence E.; Meehan, Thomas K.

2011-01-01

440

Gauge Freedom in Orbital Mechanics  

E-print Network

In orbital and attitude dynamics the coordinates and the Euler angles are expressed as functions of the time and six constants called elements. Under disturbance, the constants are endowed with time dependence. The Lagrange constraint is then imposed to guarantee that the functional dependence of the perturbed velocity on the time and constants stays the same as in the undisturbed case. Constants obeying this condition are called osculating elements. The constants chosen to be canonical are called Delaunay elements, in the orbital case, or Andoyer elements, in the spin case. (As some Andoyer elements are time dependent even in the free-spin case, the role of constants is played by their initial values.) The Andoyer and Delaunay sets of elements share a feature not readily apparent: in certain cases the standard equations render them non-osculating. In orbital mechanics, elements furnished by the standard planetary equations are non-osculating when perturbations depend on velocities. To preserve osculation, the equations must be amended with extra terms that are not parts of the disturbing function. In the case of Delaunay parameterisation, these terms destroy canonicity. So under velocity-dependent disturbances, osculation and canonicity are incompatible. (Efroimsky and Goldreich 2003, 2004) Similarly, the Andoyer elements turn out to be non-osculating under angular-velocity-dependent perturbation. Amendment of only the Hamiltonian makes the equations render nonosculating elements. To make them osculating, more terms must enter the equations (and the equations will no longer be canonical). In practical calculations, is often convenient to deliberately deviate from osculation by substituting the Lagrange constraint with a condition that gives birth to a family of nonosculating elements.

Michael Efroimsky

2006-03-03

441

The Orbiting Carbon Observatory (OCO)  

NASA Technical Reports Server (NTRS)

CO2 is the principal human generated driver of climate change. Accurate forecasting of future climate requires an improved understanding of the global carbon cycle and its interaction with the climate system. The Orbiting Carbon Observatory (OCO) will make global, space-based observations of atmospheric CO2 with the precision, resolution, and coverage needed to understand sources and sinks. OCO data will provide critical information for decision makers including the scientific basis for policy formulation, guide for carbon management strategies and treaty monitoring.

Miller, Charles E.

2005-01-01

442

Interactive Orbit Control in MATLAB  

SciTech Connect

Recent advances in steering algorithms have made it possible to accurately control electron beam position in storage rings, implement fast and slow feedback systems, and in some cases detect hardware errors. In practice, however, the program operator would like to reduce the overhead of selecting variables and constraints and to easily view the data. To simplify the process, we constructed an interactive orbit control program in MATLAB [1]. The program modules are easily adapted to new algorithms or beam lines. This paper describes the program functionality and architecture.

Corbett, William

2001-07-06

443

Mars Climate Orbiter Mishap Report  

NSDL National Science Digital Library

This Review Panel Report represents the work of a review team contracted by NASA to analyze its programs and practices. Released this week, the report discusses findings relating to the failure of the Mars Climate Orbiter on September 23, 1999. The report also summarizes lessons learned from the mishap, gives an overview of NASA project management, identifies common themes related to recent failures, and makes recommendations for improving the likelihood of future success for NASA missions. An additional report, from the Mars Independent Assessment Team chaired by Thomas Young, will be available by the end of March.

444

Orbital debris: A technical assessment  

NASA Technical Reports Server (NTRS)

To acquire an unbiased technical assessment of (1) the research needed to better understand the debris environment, (2) the necessity and means of protecting spacecraft against the debris environment, and (3) potential methods of reducing the future debris hazard, NASA asked the National Research Council to form an international committee to examine the orbital debris issue. The committee was asked to draw upon available data and analyses to: characterize the current debris environment, project how this environment might change in the absence of new measures to alleviate debris proliferation, examine ongoing alleviation activities, explore measures to address the problem, and develop recommendations on technical methods to address the problems of debris proliferation.

Gleghorn, George; Asay, James; Atkinson, Dale; Flury, Walter; Johnson, Nicholas; Kessler, Donald; Knowles, Stephen; Rex, Dietrich; Toda, Susumu; Veniaminov, Stanislav

1995-01-01

445

Orbits of mutually unbiased bases  

E-print Network

We express Alltop's construction of mutually unbiased bases as orbits under the Weyl-Heisenberg group in prime dimensions and find a related construction in dimensions 2 and 4. We reproduce Alltop's mutually unbiased bases using abelian subgroups of the Clifford group in prime dimensions, in direct analogy to the well-known construction of mutually unbiased bases using abelian subgroups of the Weyl-Heisenberg group. Finally, we prove three theorems relating to the distances and linear dependencies among different sets of mutually unbiased bases.

Kate Blanchfield

2014-03-25

446

Pearls of Orbital Trauma Management  

PubMed Central

Orbital fractures account for a significant portion of traumatic facial injuries. Although plastic surgery literature is helpful, additional pearls and insights are provided in this article from the experience of an oculoplastic surgeon. The fundamentals remain the same, but the perceptions differ and provide a healthy perspective on a long-standing issue. The most important thing to remember is that the optimal management plan is often variable, and the proper choice regarding which plan to choose rests upon the clinical scenario and the surgeon having an honest perception of his or her level of expertise and comfort level. PMID:22550464

Roth, Forrest S.; Koshy, John C.; Goldberg, Jonathan S.; Soparkar, Charles N.S.

2010-01-01

447

Environmental dynamics at orbital altitudes  

NASA Technical Reports Server (NTRS)

The work reported involved the improvement of aerodynamic theory for free molecular and transition flow regimes. The improved theory was applied to interpretation of the dynamic response of objects traveling through the atmosphere. Satellite drag analysis includes analysis methods, atmospheric super rotation effects, and satellite lift effects on orbital dynamics. Transition flow regimes were studied with falling sphere data and errors resulting in inferred atmospheric parameters from falling sphere techniques. Improved drag coefficients reveal considerable error in previous falling sphere data. The drag coefficient has been studied for the entire spectrum of Knudsen Number and speed ratio, with particular emphasis on the theory of the very low-speed ratio regime.

Karr, G. R.

1976-01-01

448

Satellite physical and orbital characteristics  

NASA Technical Reports Server (NTRS)

Perhaps sixty satellites received sufficient tracking to warrant their consideration for inclusion in the current gravity field development activities underway for TOPEX. These objects vary in size, shape, and in their orbital history -- and in the information available concerning any and all of these characteristics. An attempt to obtain initial information on the satellite physical characteristics and the overall size of nongravitational perturbations for each of the satellites under consideration. Atmospheric drag perturbations were modeled and a solution for zonal harmonics was made. Calibrated area-to-mass ratios and estimates of nonconservative force accelerations are tabulated.

Klosko, S. M.

1985-01-01

449

Lunar resource surveys from orbit  

NASA Technical Reports Server (NTRS)

The chemical composition of lunar soil and rocks is known now for nine surface sites, by analysis of returned samples. Three classes of silicate material, mare basalt, KREEP, and highland material (sometimes called ANT) have been identified as major components. Gamma-ray and X-ray instruments have mapped the Apollo 15 and 16 ground tracks for major elements, K, and Th. It is hoped that the Lunar Polar Orbiter will carry instruments capable of producing a chemical map of the entire moon. The most exciting possibility is that ice may exist in shadowed regions near the lunar pole.

Arnold, J. R.

1977-01-01

450

Orbiter fuel cell improvement assessment  

NASA Technical Reports Server (NTRS)

The history of fuel cells and the theory of fuel cells is given. Expressions for thermodynamic and electrical efficiencies are developed. The voltage losses due to electrode activation, ohmic resistance and ionic diffusion are discussed. Present limitations of the Orbiter Fuel Cell, as well as proposed enhancements, are given. These enhancements are then evaluated and recommendations are given for fuel cell enhancement both for short-range as well as long-range performance improvement. Estimates of reliability and cost savings are given for enhancements where possible.

Johnson, R. E.

1981-01-01

451

PHOTOMETRIC ORBITS OF EXTRASOLAR PLANETS  

SciTech Connect

We define and analyze the photometric orbit (PhO) of an extrasolar planet observed in reflected light. In our definition, the PhO is a Keplerian entity with six parameters: semimajor axis, eccentricity, mean anomaly at some particular time, argument of periastron, inclination angle, and effective radius, which is the square root of the geometric albedo times the planetary radius. Preliminarily, we assume a Lambertian phase function. We study in detail the case of short-period giant planets (SPGPs) and observational parameters relevant to the Kepler mission: 20 ppm photometry with normal errors, 6.5 hr cadence, and three-year duration. We define a relevant 'planetary population of interest' in terms of probability distributions of the PhO parameters. We perform Monte Carlo experiments to estimate the ability to detect planets and to recover PhO parameters from light curves. We calibrate the completeness of a periodogram search technique, and find structure caused by degeneracy. We recover full orbital solutions from synthetic Kepler data sets and estimate the median errors in recovered PhO parameters. We treat in depth a case of a Jupiter body-double. For the stated assumptions, we find that Kepler should obtain orbital solutions for many of the 100-760 SPGP that Jenkins and Doyle estimate Kepler will discover. Because most or all of these discoveries will be followed up by ground-based radial velocity observations, the estimates of inclination angle from the PhO may enable the calculation of true companion masses: Kepler photometry may break the 'msin i' degeneracy. PhO observations may be difficult. There is uncertainty about how low the albedos of SPGPs actually are, about their phase functions, and about a possible noise floor due to systematic errors from instrumental and stellar sources. Nevertheless, simple detection of SPGPs in reflected light should be robust in the regime of Kepler photometry, and estimates of all six orbital parameters may be feasible in at least a subset of cases.

Brown, Robert A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)], E-mail: rbrown@stsci.edu

2009-09-10

452

Mission Design for the Lunar Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

The Lunar Reconnaissance Orbiter (LRO) will be the first mission under NASA's Vision for Space Exploration. LRO will fly in a low 50 km mean altitude lunar polar orbit. LRO will utilize a direct minimum energy lunar transfer and have a launch window of three days every two weeks. The launch window is defined by lunar orbit beta angle at times of extreme lighting conditions. This paper will define the LRO launch window and the science and engineering constraints that drive it. After lunar orbit insertion, LRO will be placed into a commissioning orbit for up to 60 days. This commissioning orbit will be a low altitude quasi-frozen orbit that minimizes stationkeeping costs during commissioning phase. LRO will use a repeating stationkeeping cycle with a pair of maneuvers every lunar sidereal period. The stationkeeping algorithm will bound LRO altitude, maintain ground station contact during maneuvers, and equally distribute periselene between northern and southern hemispheres. Orbit determination for LRO will be at the 50 m level with updated lunar gravity models. This paper will address the quasi-frozen orbit design, stationkeeping algorithms and low lunar orbit determination.

Beckman, Mark

2007-01-01

453

Orbital evolution. [of large natural satellite  

NASA Technical Reports Server (NTRS)

The orbital evolution of a large satellite is governed primarily by tidal interactions between the satellite and the planet it orbits. Tides raised on a planet by a satellite transfer energy and angular momentum to the satellite orbit; this changes the semimajor axes of satellite orbits, increasing the size of those orbits where the satellite mean motion is smaller than the planetary angular velocity, and decreasing those where the opposite is true. Substantial changes caused by such tides for satellites of the terrestrial planets may explain the absence of satellites about Mercury and Venus. For Jovian and Saturnian satellites, such tides probably are only important in bringing about some of the observed orbital resonances. Tides raised on satellites generally cause decreasing orbital eccentricities, indicating why close satellites always have nearly circular orbits. Different processes of orbital evolution dominate for small bodies; their effects probably are critical in positioning material in the primordial dust cloud so that satellite coagulation may occur. A qualitative description is given of the orbital results of gas drag, radiation pressure, Poynting-Robertson drag and electromagnetic forces.

Burns, J. A.

1977-01-01

454

The Kepler Project: Mission Update  

NASA Technical Reports Server (NTRS)

Kepler is a Discovery-class mission designed to determine the frequency of Earth-size planets in and near the habitable zone of solar-like stars. The instrument consists of a 0.95 m aperture photometer designed to obtain high precision photometric measurement of > 100,000 stars to search for patterns of transits. The focal plane of the Schmidt-telescope contains 42 CCDs with at total of 95 mega pixels that cover 116 square degrees of sky. The photometer was launched into an Earth-trailing heliocentric orbit on March 6, 2009, finished its commissioning on May 12, and is now in the science operations mode. During the commissioning of the Kepler photometer, data were obtained at a 30 minute cadence for 53,000 stars for 9.7 days. Although the data have not yet been corrected for the presence of systematic errors and artifacts, the data show the presence of hundreds of eclipsing binary stars and variable stars of amazing variety. To provide some estimate of the capability of the photometer, a quick analysis of the photometric precision was made. Analysis of the commissioning data also show transits, occultations and light emitted from the known exoplanet HAT-P7b. The data show a smooth rise and fall of light: from the planet as it orbits its star, punctuated by a drop of 130 +/- 11 ppm in flux when the planet passes behind its star. We interpret this as the phase variation of the dayside thermal emission plus reflected light from the planet as it orbits its star and is occulted. The depth of the occultation is similar in amplitude to that expected from a transiting Earth-size planet and demonstrates that the Mission has the precision necessary to detect such planets.

Borucki, William J.; Koch, David G.

2009-01-01

455

Dexterous Orbital Servicing System (DOSS)  

NASA Technical Reports Server (NTRS)

The Dexterous Orbiter Servicing System (DOSS) is a dexterous robotic spaceflight system that is based on the manipulator designed as part of the Flight Telerobotics Servicer program for the Space Station Freedom and built during a 'technology capture' effort that was commissioned when the FTS was cancelled from the Space Station Freedom program. The FTS technology capture effort yielded one flight manipulator and the 1 g hydraulic simulator that had been designed as an integrated test tool and crew trainer. The DOSS concept was developed to satisfy needs of the telerobotics research community, the space shuttle, and the space station. As a flight testbed, DOSS would serve as a baseline reference for testing the performance of advanced telerobotics and intelligent robotics components. For shuttle, the DOSS, configured as a movable dexterous tool, would be used to provide operational flexibility for payload operations and contingency operations. As a risk mitigation flight demonstration, the DOSS would serve the International Space Station to characterize the end to end system performance of the Special Purpose Dexterous Manipulator performing assembly and maintenance tasks with actual ISSA orbital replacement units. Currently, the most likely entrance of the DOSS into spaceflight is a risk mitigation flight experiment for the International Space Station.

Price, Charles R.; Berka, Reginald B.; Chladek, John T.

1994-01-01

456

Orbital inflammation after dental procedures.  

PubMed

This study reports 3 cases of acute orbital inflammation that occurred within 3 weeks of various dental procedures and offers a possible mechanism as to their cause. The charts of 3 patients were retrospectively examined. Clinical notes, laboratory testing, and imaging studies were reviewed. The cases involved a 36-year old woman, a 61-year-old woman, and a 44-year-old woman who developed acute dacryoadenitis after tooth extraction in the former case and after routine dental cleaning in the latter 2. All cases were initially treated with an oral steroid taper over 6 to 8 weeks. The first 2 cases resolved promptly and have remained quiescent. The last individual had recurrent symptoms prompting lacrimal gland biopsy that demonstrated chronic, nongranulomatous inflammation without monoclonality. The patient subsequently responded to periorbital steroid injection only to have a recurrent bout of inflammation after repeat dental cleaning. Another periorbital steroid injection resulted in resolution of inflammation. The authors propose that a subset of acute orbital inflammation may represent an autoimmune response triggered by dental manipulation. These cases are suggestive of an atypical variant of noninfectious, microbe-induced inflammation. PMID:22391741

Choe, Christina H; Eckstein, Lauren A; Vagefi, M Reza

2012-01-01

457

On-orbit Passive Thermography  

NASA Technical Reports Server (NTRS)

On July 12, 2006, British-born astronaut Piers Sellers became the first person to conduct thermal nondestructive evaluation experiments in space, demonstrating the feasibility of a new tool for detecting damage to the reinforced carbon-carbon (RCC) structures of the Shuttle. This new tool was an EVA (Extravehicular Activity, or spacewalk) compatible infrared camera developed by NASA engineers. Data was collected both on the wing leading edge of the Orbiter and on pre-damaged samples mounted in the Shuttle s cargo bay. A total of 10 infrared movies were collected during the EVA totaling over 250 megabytes of data. Images were downloaded from the orbiting Shuttle to Johnson Space Center for analysis and processing. Results are shown to be comparable to ground-based thermal inspections performed in the laboratory with the same type of camera and simulated solar heating. The EVA camera system detected flat-bottom holes as small as 2.54cm in diameter with 50% material loss from the back (hidden) surface in RCC during this first test of the EVA IR Camera. Data for the time history of the specimen temperature and the capability of the inspection system for imaging impact damage are presented.

Howell, Patricia A.; Winfree, William P.; Cramer, K. Elliott

2008-01-01

458

Orbital Debris Observations with WFCAM  

NASA Astrophysics Data System (ADS)

The United Kingdom Infrared Telescope has been operating for 35 years on the summit of Mauna Kea as a premier Infrared astronomical facility. In its 35th year the telescope has been turned over to a new operating group consisting of University of Arizona, University of Hawaii and the LM Advanced Technology Center. UKIRT will continue its astronomical mission with a portion of observing time dedicated to orbital debris and Near Earth Object detection and characterization. During the past 10 years the UKIRT Wide Field CAMera (WFCAM) has been performing large area astronomical surveys in the J, H and K bands. The data for these surveys have been reduced by the Cambridge Astronomical Survey Unit in Cambridge, England and archived by the Wide Field Astronomy Unit in Edinburgh, Scotland. During January and February of 2014 the Wide Field CAMera (WFCAM) was used to scan through the geostationary satellite belt detecting operational satellites as well as nearby debris. Accurate photometric and astrometric parameters have been developed by CASU for each of the detections and all data has been archived by WFAU. This paper will present the January and February results of the orbital debris surveys with WFCAM.

Kendrick, R.; Mann, B.; Read, M.; Kerr, T.; Irwin, M.; Cross, N.; Bold, M.,; Varricatt, W.; Madsen, G.

2014-09-01

459

Constrained orbital intercept-evasion  

NASA Astrophysics Data System (ADS)

An effective characterization of intercept-evasion confrontations in various space environments and a derivation of corresponding solutions considering a variety of real-world constraints are daunting theoretical and practical challenges. Current and future space-based platforms have to simultaneously operate as components of satellite formations and/or systems and at the same time, have a capability to evade potential collisions with other maneuver constrained space objects. In this article, we formulate and numerically approximate solutions of a Low Earth Orbit (LEO) intercept-maneuver problem in terms of game-theoretic capture-evasion guaranteed strategies. The space intercept-evasion approach is based on Liapunov methodology that has been successfully implemented in a number of air and ground based multi-player multi-goal game/control applications. The corresponding numerical algorithms are derived using computationally efficient and orbital propagator independent methods that are previously developed for Space Situational Awareness (SSA). This game theoretical but at the same time robust and practical approach is demonstrated on a realistic LEO scenario using existing Two Line Element (TLE) sets and Simplified General Perturbation-4 (SGP-4) propagator.

Zatezalo, Aleksandar; Stipanovic, Dusan M.; Mehra, Raman K.; Pham, Khanh

2014-06-01

460

Achromatic orbital angular momentum generator  

NASA Astrophysics Data System (ADS)

We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of two glued hollow axicons, is used to introduce a nonuniform rotation of polarization into a linearly polarized input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarization, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of 95% for these three different wavelengths is observed. This device may find applications in imaging from micro- to astronomical systems where a white vortex beam is needed.

Bouchard, Frédéric; Mand, Harjaspreet; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W.

2014-12-01

461

Safety in earth orbit study. Volume 4: Space shuttle orbiter: Safety requirements and guidelines on-orbit phase  

NASA Technical Reports Server (NTRS)

Safety requirements and guidelines are listed for the space shuttle orbiter and for its interface with other vehicles. The requirements and guidelines are specific to the hazards and emergencies in earth orbit. The requirements and guidelines for the orbiter are those with respect to vehicle design, safety devices, warning devices, operational procedures, and residual hazards. The requirements and guidelines for interface with the space station, upper stage vehicles, and sortie payloads are imposed on these vehicles to ensure the safety of the shuttle orbiter. The rationale for the safety requirements and guidelines is also discussed.

1972-01-01

462

Orbit Design of Earth-Observation Satellite  

NASA Astrophysics Data System (ADS)

The purpose of this study is to design a reliable orbit for a medium-resolution scientific satellite to observe Earth for developmental issues such as water resources, agricultural, and industrial. To meet this objective this study firstly, defines the mission, secondly, determines mission constraints, thirdly, design the attitude and orbit control system. As for the observation requirements, and the revisit time are provided as a function of the orbital parameters. Initial orbital parameters are obtained by optimal analysis between observation characteristics and attitude and orbit maintenance costs. Long term station-keeping strategies will be provided for the proposed solutions. Impulsive control will be investigated to provide a reliable and affordable attitude and orbit control system.

Owis, Ashraf

463

Orbital Granulomatosis With Polyangiitis (Wegener Granulomatosis)  

PubMed Central

The pathology of granulomatosis with polyangiitis (GPA), formerly Wegener granulomatosis, typically features a granulomatous and sometimes necrotizing vasculitis targeting the respiratory tract and kidneys. However, orbital involvement occurs in up to 60% of patients and is frequently the first or only clinical presentation in patients with systemic or limited forms of GPA. Orbital GPA can cause significant morbidity and potentially lead to complete loss of vision and permanent facial deformity. Fortunately, GPA is highly responsive to medical treatment with corticosteroids combined with cyclophosphamide or, more recently, rituximab. Therefore, it is imperative for this disease to be accurately diagnosed on orbital biopsy and distinguished from other histologically similar orbital lesions. Herein, we review the clinical and pathologic findings of orbital GPA, focusing on the differentiation of this disease from other inflammatory orbital lesions. PMID:25076302

Muller, Karra; Lin, Jonathan H.

2014-01-01

464

Orbital tumor revealing a systemic sarcoidosis.  

PubMed

Ocular involvement is seen in approximately 25% of patients with sarcoidosis. Uveitis is the most common ocular manifestation, but sarcoidosis may involve any part of the eye. Orbital manifestations of sarcoidosis are uncommon with few series in the literature. A 65-year-old woman presented with redness of the right eye and painless, unilateral eyelid swelling. Orbital scanning revealed mass infiltrating the soft tissue of the inferior right orbital quadrant. Biopsy results showed nodular, noncaseating granulomas consistent with sarcoidosis. The complete systemic workup revealed systemic manifestations of sarcoidosis at the time of examination with hilar and mediastinal lymphadenopathies noted on CT scan. The orbital surgical treatment was followed by systemic prednisone therapy with good response. Although rare, orbital sarcoidosis must be considered in the evaluation of orbital tumors in elderly patients. A search for systemic findings should be undertaken and appropriate therapy should be instituted. PMID:25796029

Hannanachi Sassi, Samia; Dhouib, Rim; Kanchal, Fatma; Doghri, Raoudha; Boujelbene, Nadia; Bouguila, Hedi; Mrad, Karima

2015-03-01

465

Ferroelectric control of orbital occupancy in manganites  

NASA Astrophysics Data System (ADS)

Recent successful fabrication of epitaxial and coherent ferroelectric/manganite interfaces makes it possible to dynamically control charge and spin in manganites [1]. We demonstrate with ab initio calculations that in this system, d-orbital occupancies of the interfacial Mn atom can also be modulated by flipping the ferroelectric polarization (i.e. flippable orbital polarization). The underlying mechanism is the structural distortions of the oxygen octahedron and the Mn atom inside induced by the ferroelectric polarization. The in-plane orbital dx^2-y^2 is stablized by rumpling in MnO2 layers, while the Jahn-Teller distortion (c/a>1) favors the out-of-plane orbital d3z^2-r^2. This ferroelectric control of orbital occupancy serves as a new approach separate from strain for engineering orbital orderings in transition metal oxides. [4pt] [1] C.A.F.Vaz et al., Phys. Rev. Lett. 104, 127202 (2010)

Chen, Hanghui; Ismail-Beigi, Sohrab

2012-02-01

466

Orbital debris characterization with impact flash signatures  

SciTech Connect

Orbital debris is recognized as a serious and growing threat to man's utilization and exploration of space. While some information is available on the material composition of orbital debris, most measurements of orbital debris size and velocity distributions do not distinguish material type. The analysis and understanding of impact flash signatures can lead to an in-situ detector system with the ability to determine size and impact velocity distribution for orbital debris segregated by material type. This detector concept is based on an understanding of how material shock properties govern the flash signature arising from the impact of a piece of orbital debris (impactor) against a witness plate (target). Analytical results are presented that identify the most promising witness plate materials with respect to producing impact flash signatures that characterize the orbital debris material. 7 refs.

Ang, J.A.

1991-01-01

467

Orbital debris characterization with impact flash signatures  

SciTech Connect

Orbital debris is recognized as a serious and growing threat to man`s utilization and exploration of space. While some information is available on the material composition of orbital debris, most measurements of orbital debris size and velocity distributions do not distinguish material type. The analysis and understanding of impact flash signatures can lead to an in-situ detector system with the ability to determine size and impact velocity distribution for orbital debris segregated by material type. This detector concept is based on an understanding of how material shock properties govern the flash signature arising from the impact of a piece of orbital debris (impactor) against a witness plate (target). Analytical results are presented that identify the most promising witness plate materials with respect to producing impact flash signatures that characterize the orbital debris material. 7